{"gene":"LY96","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":1999,"finding":"MD-2 (LY96) is physically associated with the extracellular domain of TLR4 on the cell surface and is requisite for LPS signaling by TLR4; transfection of MD-2 confers LPS responsiveness on TLR4-expressing cells that otherwise lack it.","method":"Co-immunoprecipitation, transfection-based cell activation assay (NF-κB reporter)","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — founding paper with reciprocal co-IP and functional transfection assay, replicated by multiple independent labs","pmids":["10359581"],"is_preprint":false},{"year":2002,"finding":"MD-2 knockout mice do not respond to LPS and survive endotoxic shock; in MD-2-deficient fibroblasts, TLR4 fails to reach the plasma membrane and is retained in the Golgi apparatus, demonstrating that MD-2 is essential for correct intracellular trafficking and plasma membrane localization of TLR4.","method":"MD-2 knockout mouse (in vivo LPS challenge, Salmonella infection); subcellular fractionation and microscopy of embryonic fibroblasts","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout with defined in vivo phenotype plus direct localization experiment; independently confirmed across multiple studies","pmids":["12055629"],"is_preprint":false},{"year":2001,"finding":"MD-2 directly binds LPS (apparent KD ~65 nM) independently of LBP and CD14; LBP competes with MD-2 for LPS binding, establishing MD-2 as a genuine LPS-binding protein.","method":"Recombinant protein production, five independent binding assays (including equilibrium binding with Kd determination); competition assay with LBP","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct in vitro binding assay with recombinant protein and Kd measurement, multiple orthogonal binding assays in one study","pmids":["11500507"],"is_preprint":false},{"year":2001,"finding":"LPS is cross-linked directly to both TLR4 and MD-2 (and CD14) when co-expressed with CD14, demonstrating LPS is in close proximity to each member of the tripartite receptor complex; CD14 is required for LPS transfer to TLR4 and MD-2.","method":"Radioiodinated photoactivatable LPS cross-linking assay in transiently transfected HEK293 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct covalent photocrosslinking with radiolabeled LPS, chemical crosslinking with functional validation, single lab but multiple orthogonal approaches","pmids":["11274165"],"is_preprint":false},{"year":2007,"finding":"Crystal structure of human MD-2 (2.0 Å) reveals a deep hydrophobic cavity formed by two beta-sheets; in complex with tetra-acylated lipid IVa, all four acyl chains are fully enclosed in this cavity with the phosphorylated glucosamine moieties at the cavity entrance, establishing MD-2 as the principal endotoxin-binding subunit.","method":"X-ray crystallography at 2.0 Å (apo MD-2) and 2.2 Å (lipid IVa complex)","journal":"Science (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structures of both apo and ligand-bound forms; foundational structural paper replicated by subsequent structures","pmids":["17569869"],"is_preprint":false},{"year":2009,"finding":"Crystal structure of the TLR4-MD-2-LPS complex at ~3 Å resolution reveals an m-shaped 2:2:2 receptor multimer; five of six LPS lipid chains are buried in MD-2's hydrophobic pocket while the sixth is exposed and contacts conserved TLR4 phenylalanines; LPS directly bridges two TLR4-MD-2 units; the MD-2 F126 loop undergoes localized conformational change to support TLR4 dimerization; phosphate groups of LPS form ionic interactions with positively charged residues in TLR4 and MD-2 to stabilize the active complex.","method":"X-ray crystallography of TLR4-MD-2-LPS complex","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — landmark crystal structure of full receptor complex, independently confirmed by subsequent mouse TLR4/MD-2/LPS structure","pmids":["19252480"],"is_preprint":false},{"year":2004,"finding":"Purified monomeric endotoxin-MD-2 complex (generated by sequential transfer from LBP→sCD14→MD-2) activates TLR4-expressing cells at picomolar endotoxin concentrations; excess free MD-2 inhibits delivery of the endotoxin-MD-2 complex to TLR4 cells, establishing ordered sequential transfer as the mechanism for high-sensitivity LPS detection.","method":"Purification of recombinant endotoxin-MD-2 complex; TLR4-dependent cell activation assay; inhibition studies with excess soluble MD-2","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — biochemical reconstitution with purified components, functional validation in cell assay with competition controls, single lab with multiple orthogonal approaches","pmids":["15010525"],"is_preprint":false},{"year":2003,"finding":"Cell surface LPS-TLR4-MD-2 complexes form with a Kd ~3 nM; CD14 greatly enhances LPS loading onto TLR4-MD-2 but is not retained in the final complex; detergent disrupts LPS-CD14 but not LPS-TLR4-MD-2 interaction.","method":"Co-immunoprecipitation of LPS-TLR4-MD-2 complexes from cell surface; competition binding with lipid A antagonist E5531; Kd estimation","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct binding measurement with Kd, reciprocal precipitation, and pharmacological competition; single lab with multiple orthogonal methods","pmids":["14517279"],"is_preprint":false},{"year":2001,"finding":"MD-2 exists predominantly as large disulfide-linked oligomers in solution; monomeric MD-2 preferentially binds TLR4 and confers LPS responsiveness more efficiently than multimeric forms; MD-2 associates with TLR4 in the ER/cis-Golgi before being secreted.","method":"Secreted MD-2 characterization by SDS-PAGE, TLR4 binding assays; LPS responsiveness reporter assay; subcellular fractionation","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical characterization with multiple methods (SDS-PAGE, functional assays, fractionation) in a single lab study","pmids":["11593030"],"is_preprint":false},{"year":2001,"finding":"N-linked glycosylation at Asn26 and Asn114 of MD-2 is not required for cell surface expression, but the double glycosylation mutant of MD-2 fails to support LPS-induced NF-κB activation, IL-8 secretion, or JNK activation, demonstrating that N-linked carbohydrates of MD-2 are essential for functional LPS receptor integrity.","method":"Site-directed mutagenesis of N-glycosylation sites; UV-crosslinking LPS binding assay; NF-κB/IL-8/JNK activation assays in transfected HeLa cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — site-directed mutagenesis combined with multiple functional readouts (crosslinking, reporter, cytokine, kinase) in single study","pmids":["11706042"],"is_preprint":false},{"year":2003,"finding":"Lysines 128 and 132 of MD-2 are required for LPS binding; MD-2 must be surface-bound to TLR4 before LPS binding and TLR4 receptor cluster formation can occur; CD14 enhances LPS binding to MD-2 but is not essential for cellular activation.","method":"Site-directed mutagenesis; LPS binding assay; confocal microscopy of TLR4 clustering; NF-κB reporter assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — mutagenesis with direct LPS-binding assay and visual receptor clustering readout, multiple orthogonal methods in single study","pmids":["12960171"],"is_preprint":false},{"year":2003,"finding":"Separate domains of human MD-2 mediate TLR4 binding and LPS responsiveness; Cys95 and Cys105 (forming an intramolecular disulfide) and surrounding residues (R90, K91, D100, Y102) are required for TLR4 binding; a distinct basic/aromatic region is responsible for conferring LPS responsiveness.","method":"Site-directed mutagenesis; co-immunoprecipitation; NF-κB reporter assay; dominant-negative inhibition in primary endothelial cells","journal":"Journal of immunology (Baltimore, Md. : 1950)","confidence":"High","confidence_rationale":"Tier 1 / Moderate — systematic mutagenesis mapping two distinct functional domains with both binding and signaling readouts","pmids":["14607928"],"is_preprint":false},{"year":2003,"finding":"The intramolecular disulfide bond between Cys95 and Cys105 of MD-2 is essential for LPS responsiveness; substitution of either Cys95 or Cys105 alone abolishes activity, whereas simultaneous substitution of both partially restores it; most Cys residues can participate in intermolecular oligomer formation.","method":"17 single and multiple Cys-to-Ser substitution mutants analyzed by SDS-PAGE and NF-κB reporter assay; structural analysis of disulfide connectivity","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — systematic mutagenesis of all seven Cys residues with structural and functional characterization in single study","pmids":["12642668"],"is_preprint":false},{"year":2001,"finding":"Human MD-2 determines species-specific LPS recognition: hMD-2 confers responsiveness to lipid A but not to lipid IVa when associated with mouse TLR4, whereas mouse MD-2 confers responsiveness to both, demonstrating that MD-2 directly controls the fine ligand specificity of TLR4.","method":"Chimeric receptor (mTLR4/hMD-2) transfection and NF-κB activation assay; pharmacological analysis with lipid IVa as agonist/antagonist probe","journal":"International immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — species-chimeric receptor approach with clear mechanistic conclusion; replicated by subsequent crystal structures and mutagenesis studies","pmids":["11717200"],"is_preprint":false},{"year":2000,"finding":"Co-expression of mouse TLR4 and mouse MD-2 is required for Taxol-induced NF-κB signaling; human TLR4/hMD-2 does not confer Taxol responsiveness; an LPS antagonist also blocks Taxol-induced signaling via TLR4/MD-2, indicating TLR4/MD-2 is the shared signaling complex for both Taxol and LPS in mice and that species specificity resides in MD-2.","method":"Ba/F3 transfectants expressing species-specific TLR4/MD-2 combinations; NF-κB reporter assay; pharmacological blockade","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean transfection model with species chimeras, pharmacological validation, replicated in a follow-up study (PMID 11581576)","pmids":["10644670","11581576"],"is_preprint":false},{"year":2008,"finding":"Paclitaxel binds directly to recombinant human MD-2 protein (dose-dependent, blocked by anti-MD-2 antibody); murine MD-2, not human MD-2, is required for TLR4 activation by paclitaxel; species-specific differences in pocket size, surface charge, and position of binding within the MD-2 pocket — particularly involving Phe126 as a dimerization bridge — explain species specificity.","method":"ELISA-based binding assay with recombinant hMD-2; HEK293 transfections with human/murine TLR4/MD-2 chimeras; computational docking to crystal structures","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding assay with antibody inhibition plus chimeric receptor functional study; computational docking is supportive but not definitive","pmids":["18650420"],"is_preprint":false},{"year":2002,"finding":"TLR4-CD14-MD-2 complexes rapidly and constitutively recycle between the plasma membrane and the Golgi apparatus; LPS follows these trafficking pathways in CD14-positive cells; MyD88 translocates to the cell surface upon LPS exposure; Golgi-localized TLR4 is not required for LPS signaling (brefeldin A disrupts Golgi TLR4 but preserves signaling).","method":"Fluorescent TLR4 live-cell confocal imaging; brefeldin A treatment; MyD88 translocation assay; cross-linking-induced signaling","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct live-cell imaging with pharmacological dissection; multiple orthogonal approaches in single study","pmids":["12324469"],"is_preprint":false},{"year":2006,"finding":"MD-2 residues Phe126 and Gly129 are required for LPS-induced TLR4 receptor clustering but not for LPS binding; Gly59 is a novel critical residue for LPS binding; receptor clustering and LPS-receptor dissociation depend on TLR4 signaling and require endosomal acidification.","method":"MD-2 alanine-scanning mutagenesis; LPS binding assay; TLR4 clustering assay by microscopy; pharmacological blockade of endosomal acidification","journal":"Journal of immunology (Baltimore, Md. : 1950)","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — systematic mutagenesis dissecting binding from clustering with multiple orthogonal readouts","pmids":["16670331"],"is_preprint":false},{"year":2009,"finding":"Hydrophobic residues Val82, Met85, and Leu87 in the MD-2 hairpin loop (β5–β6) are essential for transfer of endotoxin from CD14 to monomeric MD-2 and for TLR4 activation; conserved hydrophobic residues Phe440 and Phe463 in TLR4 LRR16–17 are also essential for activation; these residues form a hydrophobic interface between the exposed acyl chain of LPS-bound MD-2 and the neighboring TLR4.","method":"Site-directed mutagenesis of MD-2 and TLR4; endotoxin transfer assay from CD14 to MD-2; NF-κB reporter assay in transfected cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — systematic mutagenesis of both MD-2 and TLR4 with defined biochemical transfer assay plus signaling readout; consistent with crystal structure","pmids":["19321453"],"is_preprint":false},{"year":2012,"finding":"Crystal structures of mouse TLR4/MD-2/LPS (2.5 Å) and TLR4/MD-2/lipid IVa (2.7 Å) complexes show that lipid IVa in mouse MD-2 occupies nearly the same space as LPS and induces an agonistic 2:2:2 complex similar to LPS; human MD-2 binds lipid IVa in a completely different, antagonistic manner, providing structural basis for species-specific agonism/antagonism.","method":"X-ray crystallography of mouse TLR4/MD-2/LPS and TLR4/MD-2/lipid IVa complexes","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structures of both agonist and antagonist complexes in the same study, consistent with prior human structures","pmids":["22532668"],"is_preprint":false},{"year":2016,"finding":"Neoseptin-3, a peptidomimetic with no structural similarity to LPS, activates mouse TLR4/MD-2 by binding as an asymmetrical dimer within the MD-2 hydrophobic pocket; crystal structure at 2.57 Å shows an active 2:2 receptor complex similar to lipid A; activation is CD14-independent and triggers canonical MyD88- and TRIF-dependent signaling.","method":"X-ray crystallography at 2.57 Å; NF-κB/IRF3 reporter assays; MyD88/TRIF knockout validation; CD14-independence experiments","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus genetic validation with knockout cells and multiple signaling pathway readouts","pmids":["26831104"],"is_preprint":false},{"year":2021,"finding":"Short-chain sulfatides directly bind the MD-2 hydrophobic pocket and activate mouse TLR4-MD-2 (MyD88- and TRIF-dependent) independently of CD14; crystal structure of mouse TLR4-MD-2/C16-sulfatide at 2.6 Å shows three sulfatide molecules in the MD-2 pocket inducing an active 2:2 complex; sulfatides antagonize human TLR4-MD-2, with agonism/antagonism dependent on the sulfate group and inversely related to FA chain length.","method":"Crystal structure; macrophage activation assays; MyD88/TRIF-knockout validation; structure-activity relationship with sulfatide variants","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure of endogenous lipid-MD-2 complex combined with genetic (KO) and pharmacological validation","pmids":["34290146"],"is_preprint":false},{"year":2007,"finding":"Curcumin binds MD-2 at submicromolar affinity in its hydrophobic pocket (fluorescence blue-shift assay); the binding site overlaps with LPS; curcumin inhibits both MyD88-dependent and -independent TLR4 signaling; C133F mutant MD-2 retains curcumin binding, and curcumin does not form a covalent bond to the free thiol of MD-2.","method":"Fluorescence spectroscopy; competition binding with LPS; NF-κB reporter assay; C133F mutagenesis","journal":"Journal of leukocyte biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding assay with spectroscopic evidence plus functional mutagenesis, single lab","pmids":["17609337"],"is_preprint":false},{"year":2023,"finding":"Disulfiram (DSF) covalently modifies Cys133 of MD-2, blocking LPS-induced TLR4 dimerization, cell surface expression, and downstream NF-κB/IRF3 signaling; this mechanism suppresses inflammatory cytokine/interferon production by macrophages in vitro and reduces neuroinflammation and dopaminergic neuron loss in an MPTP mouse model of Parkinson's disease.","method":"Covalent modification identification; TLR4 dimerization assay; NF-κB/IRF3 reporter; macrophage cytokine assay; MPTP mouse model in vivo","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — covalent modification of defined residue with multiple orthogonal functional assays (in vitro and in vivo), single study","pmids":["37487070"],"is_preprint":false},{"year":2004,"finding":"Structural model of MD-2 (based on NPC2/Der p2 homology) predicted a beta-sandwich hydrophobic pocket; two basic residue clusters (Lys89-Arg90-Lys91 and Lys125-Lys132) are required for LPS signal transduction upon co-expression with TLR4 or as soluble protein added to TLR4-expressing cells; a peptide spanning the Cys95-Cys105 loop inhibited LPS-induced TNF-α and IL-8 production.","method":"Homology modeling; CD spectroscopy (confirming beta-sheet content); site-directed mutagenesis; NF-κB reporter assay; TNF-α/IL-8 inhibition with synthetic peptide","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis with functional validation plus peptide inhibition, but structural model is computational; corroborated by later crystal structures","pmids":["15111623"],"is_preprint":false},{"year":2001,"finding":"MD-2 physically associates with TLR2 (in addition to TLR4), enabling TLR2 to respond to LPS and lipid A structures that are otherwise non-activating; the MD-2-TLR2 interaction is weaker than the MD-2-TLR4 interaction; MD-2 enhances expression of both TLR2 and TLR4.","method":"Co-immunoprecipitation; NF-κB reporter assays in transfected cells; flow cytometry for surface expression","journal":"Journal of immunology (Baltimore, Md. : 1950)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP demonstrating physical association plus functional transfection assays, single lab study","pmids":["11160242"],"is_preprint":false},{"year":2004,"finding":"Structural regions 57-79 and 108-135 of MD-2 determine the agonist-antagonist activity of lipid IVa; single amino acid substitutions at Thr57, Val61, and Glu122 in mouse MD-2 impair lipid IVa agonism while preserving LPS (E. coli lipid A) activation.","method":"Human/mouse chimeric MD-2 expression; NF-κB reporter assay in HEK293 cells; point mutagenesis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic chimeric and point mutagenesis with clear functional readout, single lab","pmids":["16407172"],"is_preprint":false},{"year":2010,"finding":"MD-2 residues Tyr42, Arg69, Asp122, and Leu125 determine lipid IVa species specificity; E122K mutation in mouse MD-2 substantially reduces lipid IVa response; combining MD-2 and TLR4 charge-reversal mutations can completely convert murine receptor response to a human-like pattern (and vice versa), demonstrating that MD-2 surface charges at two distinct interfaces (pocket entrance and MD-2/TLR4 contact surface) govern species-specific activation.","method":"Site-directed mutagenesis; stable TLR4-expressing cell lines; purified monomeric MD-2; MD-2-deficient bone marrow macrophages; NF-κB reporter assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — systematic combinatorial mutagenesis of both MD-2 and TLR4 with primary cell validation, single study with multiple orthogonal approaches","pmids":["20592019"],"is_preprint":false},{"year":2009,"finding":"Morphine and structurally diverse opioids activate TLR4 signaling non-stereoselectively; in silico docking indicates opioids bind preferentially to the LPS-binding pocket of MD-2 rather than TLR4; naloxone blocks this signaling non-stereoselectively; TLR4 knockout mice show a threefold leftward shift in morphine analgesia dose-response.","method":"In vitro TLR4 reporter assay; pharmacological blockade (naloxone, classical TLR4 antagonist); TLR4 knockout mouse; in silico docking to MD-2 pocket","journal":"Brain, behavior, and immunity","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro functional assay plus knockout mouse validation; docking is computational and supportive only; single lab","pmids":["19679181"],"is_preprint":false},{"year":2013,"finding":"Serum amyloid A3 (SAA3) synthetic peptide (aa 20-86) directly binds MD-2 (not TLR4) with KD ~2.2 μM as measured by surface plasmon resonance; FLAG-tagged SAA3 co-precipitates with protein A-tagged MD-2 in baculovirus co-infection experiments; SAA3-MD-2 interaction activates MyD88-dependent TLR4 signaling (p38, NF-κB, Rho GTPase) but not TRIF-dependent IFN-β.","method":"Surface plasmon resonance; co-immunoprecipitation in baculovirus system; NF-κB/p38 activation assays; TLR4/MyD88 KO validation","journal":"Journal of immunology (Baltimore, Md. : 1950)","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — direct binding measurement (SPR with KD) plus co-IP and genetic (KO) validation in single study","pmids":["23858030"],"is_preprint":false},{"year":2017,"finding":"Soluble CD83 (sCD83) binds MD-2 as a high-affinity partner; sCD83 binding to MD-2 on monocytes rapidly degrades IRAK-1 and induces anti-inflammatory mediators (IDO, IL-10, PGE2 via COX-2), leading to T cell unresponsiveness.","method":"Pull-down/co-IP identifying MD-2 as sCD83 binding partner; IRAK-1 degradation assay; IDO/IL-10/PGE2 measurement; T cell proliferation assay","journal":"Journal of immunology (Baltimore, Md. : 1950)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — binding partner identification plus functional signaling characterization, single lab study","pmids":["28193829"],"is_preprint":false},{"year":2014,"finding":"PTX3 directly binds MD-2 in vitro; in MD-2-knockout mice, PTX3 fails to confer immune protection against Aspergillus fumigatus; MD-2-competent PMN adoptive transfer restores protection; PTX3-opsonized conidia activate TLR4/MD-2/TRIF-dependent signaling converging on IL-10.","method":"In vitro binding assay (PTX3-MD-2); MD-2 knockout mouse model; adoptive transfer of MD-2-competent PMN; cytokine profiling","journal":"Journal of immunology (Baltimore, Md. : 1950)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro binding plus genetic (KO) and adoptive transfer in vivo validation; single lab","pmids":["25049357"],"is_preprint":false},{"year":2013,"finding":"Globotetraosylceramide (Gb4) binds to TLR4-MD-2 (co-precipitated with recombinant MD-2; confirmed by native PAGE and docking); Gb4 competes with LPS for TLR4-MD-2 binding; A4galt-deficient mice lacking Gb4 show increased LPS sensitivity; exogenous Gb4 protects mice from LPS-induced mortality.","method":"Co-precipitation of Gb4 with recombinant MD-2; native PAGE; A4galt-knockout mouse; in vivo LPS challenge; gene expression assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding demonstrated biochemically plus KO mouse model; docking is computational; single lab","pmids":["23471986"],"is_preprint":false},{"year":2020,"finding":"Heme binds MD-2 and activates TLR4 signaling; MD-2 is required for heme-mediated NF-κB activation (absent without MD-2); heme binding site involves residues W23 and Y34 (mutagenesis reduces heme pull-down and NF-κB response); site Y36A increases heme-induced NF-κB signaling without affecting LPS response.","method":"Heme-agarose/biotin-heme pull-down of recombinant MD-2; UV/visible spectroscopy; site-directed mutagenesis; NF-κB luciferase reporter in HEK293; in silico docking","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — direct binding assays plus mutagenesis identifying binding residues, with multiple orthogonal methods; single lab study","pmids":["32695117"],"is_preprint":false},{"year":2002,"finding":"Monomeric recombinant MD-2 can interact with the soluble extracellular domain of TLR4 in solution; MD-2's ability to confer LPS responsiveness and to bind TLR4 are strongly associated; more than two intermolecular disulfide bonds stabilize MD-2 multimers.","method":"Biochemical binding assay (TLR4 ectodomain-MD-2 interaction in solution); site-directed mutagenesis of Cys residues; NF-κB reporter assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding assay with recombinant proteins plus mutagenesis, single lab","pmids":["11976338"],"is_preprint":false},{"year":2011,"finding":"Intracellular TLR4/MD-2 (present in the absence of cell-surface TLR4) can sense phagocytosed gram-negative bacteria and activate MyD88-dependent chemokine production (CCL2, CCL5) and co-stimulatory molecule upregulation (CD40, CD86) independently of TRIF/TICAM-1; intracellular TLR4/MD-2 requires PRAT4A-independent compartment; TRIF-dependent type I IFN production depends on surface TLR4.","method":"PRAT4A knockout macrophages (abolishing surface TLR4); intracellular LPS sensing assay; cytokine/chemokine measurement; co-stimulatory molecule flow cytometry","journal":"International immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO model with specific intracellular sensing readouts; single lab study","pmids":["21712422"],"is_preprint":false},{"year":2002,"finding":"MD-2 expression in intestinal epithelial cells (IECs) is regulated epigenetically; IFN-γ positively regulates the MD-2 promoter through JAK-STAT signaling (blocked by STAT inhibitor SOCS3); IFN-γ and TNF-α sensitize IECs to LPS-dependent IL-8 secretion by upregulating MD-2.","method":"RT-PCR; Western blot; MD-2 promoter reporter assay; SOCS3 overexpression; IL-8 secretion assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — promoter-reporter assay with SOCS3 dominant-negative, multiple functional readouts; single lab","pmids":["11923281"],"is_preprint":false},{"year":2009,"finding":"Epigenetic silencing (CpG methylation and histone deacetylation) of the MD-2 promoter underlies low MD-2 expression and LPS unresponsiveness in intestinal epithelial cells; inhibition of methylation (5-azacytidine) or histone deacetylation (trichostatin A) increases MD-2 mRNA expression; LPS responsiveness is polarized to the basolateral membrane of IECs.","method":"Bisulfite sequencing of MD-2 promoter; 5-azacytidine and trichostatin A treatment; MD-2 mRNA quantification; NF-κB reporter assay","journal":"Innate immunity","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct bisulfite sequencing of promoter CpG methylation plus pharmacological reversal; single lab","pmids":["19710105"],"is_preprint":false},{"year":2007,"finding":"Soluble MD-2 is a type II acute-phase protein: mRNA and protein levels rise in mouse liver during acute-phase response; IL-6 upregulates sMD-2 secretion from hepatocytes; sMD-2 binds gram-negative (but not gram-positive) bacteria and functions as an opsonin, enhancing phagocytosis by neutrophils and serving as a cofactor for TLR4-expressing cell activation by gram-negative bacteria.","method":"Mouse acute-phase response model; IL-6 stimulation of hepatocytes; bacterial binding assay; phagocytosis assay; TLR4-dependent cell activation assay","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal assays (in vivo model, cell assay, phagocytosis, bacterial binding) in single study; single lab","pmids":["18056837"],"is_preprint":false},{"year":2008,"finding":"Soluble MD-2 binds to the surface of live gram-negative bacteria; MD-2-coated bacteria show enhanced cellular activation, bacterial internalization, and intracellular killing, all in a TLR4-signaling-dependent manner (absent in Lpsd macrophages with signaling-deficient TLR4), confirming sMD-2 as an opsonin that bridges bacteria to TLR4.","method":"MD-2 binding to live bacteria (binding assay); phagocytosis/killing assays in WT vs. Lpsd macrophages; TLR4-dependence controls","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional opsonophagocytosis assay with signaling-incompetent TLR4 control; single lab","pmids":["18203953"],"is_preprint":false},{"year":2015,"finding":"The chalcone derivative L6H21 inserts into the hydrophobic pocket of MD-2, forming hydrogen bonds with Arg90 and Tyr102; it suppresses LPS-induced TLR4/MD-2 complex formation and downstream MAPK/NF-κB signaling; MD-2 knockout mice are universally protected from LPS-induced septic shock, validating MD-2 as the essential therapeutic target.","method":"SPR binding assay; ELISA; fluorescence measurement; flow cytometry; computer docking; Western blot/EMSA; MD-2 knockout mouse model","journal":"British journal of pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding with SPR plus KO mouse validation and multiple signaling readouts; single lab","pmids":["26076332"],"is_preprint":false},{"year":2021,"finding":"Zebrafish possess an MD-2 ortholog encoded by the ly96 gene; zebrafish Md-2 and Tlr4ba form a functional complex that activates NF-κB signaling in response to LPS; ly96 loss-of-function in larval zebrafish perturbs LPS-induced cytokine production, establishing an ancestral Tlr4/Md-2 LPS-sensing complex in teleosts.","method":"Bioinformatic identification; single-cell RNA sequencing; functional NF-κB reporter assay with zebrafish Md-2/Tlr4ba co-expression; ly96 loss-of-function mutation analysis","journal":"Journal of immunology (Baltimore, Md. : 1950)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional reconstitution assay plus loss-of-function genetics; single lab study on zebrafish ortholog","pmids":["33472906"],"is_preprint":false},{"year":2008,"finding":"MD-2 residues 57-66 and 82-89 (horse vs. human) and a single residue in the glycan-free flank of TLR4 solenoid determine whether lipid IVa acts as agonist or antagonist; replacing horse MD-2 residues 57-66 and 82-89 with human equivalents confers constitutive activity, suggesting conformational switching in MD-2 is important for ligand-induced activation.","method":"Horse/human chimeric MD-2 and TLR4 constructs; NF-κB reporter assay; surface charge analysis","journal":"Journal of immunology (Baltimore, Md. : 1950)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — chimeric and point-mutant receptor approach with functional signaling readout; single lab","pmids":["18606678"],"is_preprint":false},{"year":2004,"finding":"A single coding mutation in human MD-2 (Thr35Ala, A→G at position 103) results in reduced LPS-induced signaling in reporter gene assays, demonstrating that Thr35 contributes to MD-2 function.","method":"SSCP mutation screening; Lightcycler/FRET genotyping; NF-κB reporter gene assay; in vitro LPS stimulation (TNF-α measurement)","journal":"Genes and immunity","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single patient-derived mutant with reporter assay; no structural or binding characterization; single lab","pmids":["15057266"],"is_preprint":false}],"current_model":"MD-2 (LY96) is a secreted beta-sandwich glycoprotein that constitutively associates with the extracellular domain of TLR4 in the ER/Golgi, enabling TLR4 trafficking to the plasma membrane and forming the essential co-receptor for LPS recognition; LPS is transferred sequentially from LBP→CD14→MD-2, binds deeply within MD-2's hydrophobic pocket (up to five of six acyl chains buried), and the resulting LPS-MD-2 complex bridges two TLR4-MD-2 heterodimers into an active m-shaped 2:2:2 signaling complex through hydrophobic contacts between the exposed LPS acyl chain and conserved TLR4 phenylalanines (Phe440/Phe463) and ionic interactions between LPS phosphates and charged residues at the dimerization interface; distinct MD-2 surface regions mediate TLR4 binding (Cys95-Cys105 disulfide loop) versus LPS binding and receptor activation (hydrophobic pocket residues, F119/F121, K128/K132, F126/G129 for clustering), and species-specific differences in MD-2 surface charges and pocket geometry determine whether partial lipid A structures act as agonists or antagonists; beyond LPS, MD-2 serves as a direct binding site for endogenous ligands (sulfatides, Gb4, heme, SAA3, sCD83, S100A8), opioids, paclitaxel, and pharmacological inhibitors, and soluble MD-2 functions as an acute-phase opsonin for gram-negative bacteria."},"narrative":{"mechanistic_narrative":"MD-2 (LY96) is the essential LPS-binding co-receptor of the innate immune endotoxin sensor, a secreted β-sandwich glycoprotein that constitutively associates with the extracellular domain of TLR4 and renders TLR4-expressing cells responsive to LPS [PMID:10359581]. MD-2 is required for TLR4 to exit the Golgi and reach the plasma membrane, and genetic loss of MD-2 abolishes LPS responses and protects mice from endotoxic shock [PMID:12055629, PMID:26076332]. MD-2 binds LPS directly with nanomolar affinity, independently of LBP and CD14, and is the principal endotoxin-binding subunit of the receptor [PMID:11500507], its crystal structure revealing a deep hydrophobic cavity that buries the acyl chains of lipid A while presenting the phosphorylated glucosamine head groups at the cavity rim [PMID:17569869]. High-sensitivity detection proceeds by ordered, sequential transfer of endotoxin from LBP to CD14 to MD-2, producing a monomeric endotoxin–MD-2 complex that activates TLR4 at picomolar concentrations [PMID:15010525]. In the assembled TLR4–MD-2–LPS structure, five of six LPS acyl chains are enclosed in the MD-2 pocket while the exposed sixth chain and LPS phosphates bridge a second TLR4–MD-2 unit, building the active m-shaped 2:2:2 signaling complex [PMID:19252480, PMID:19321453]. Functionally distinct MD-2 surfaces separate TLR4 binding (the Cys95–Cys105 disulfide loop) from LPS binding and receptor clustering (hydrophobic pocket residues and the F126/G129 region), and species-specific differences in MD-2 pocket geometry and surface charge dictate whether partial lipid A structures such as lipid IVa act as agonists or antagonists [PMID:14607928, PMID:16670331, PMID:22532668, PMID:20592019]. Beyond LPS, the MD-2 pocket accommodates diverse exogenous and endogenous ligands—paclitaxel, sulfatides, Gb4, heme, SAA3, sCD83—and small-molecule inhibitors targeting the pocket or covalently modifying Cys133 block TLR4 activation, establishing MD-2 as a tractable anti-inflammatory drug target [PMID:18650420, PMID:34290146, PMID:37487070, PMID:23858030]. Soluble MD-2 additionally functions as an acute-phase opsonin that coats gram-negative bacteria and promotes their TLR4-dependent phagocytosis and killing [PMID:18056837, PMID:18203953].","teleology":[{"year":1999,"claim":"Established that TLR4 alone is insufficient for LPS sensing and that a physically associated partner, MD-2, is required—defining the existence of a co-receptor.","evidence":"Co-immunoprecipitation and MD-2 transfection conferring LPS responsiveness via NF-κB reporter","pmids":["10359581"],"confidence":"High","gaps":["Did not resolve whether MD-2 binds LPS directly or only stabilizes TLR4","No structural detail of the interaction"]},{"year":2001,"claim":"Showed MD-2 is itself a genuine LPS-binding protein, localizing endotoxin recognition to MD-2 rather than TLR4.","evidence":"Recombinant MD-2 binding assays with Kd determination and LBP competition","pmids":["11500507","11274165"],"confidence":"High","gaps":["Structural basis of the binding pocket not yet known","Stoichiometry within the activated receptor undefined"]},{"year":2001,"claim":"Defined MD-2 quaternary state and its trafficking origin, showing monomeric MD-2 is the functional TLR4-binding species assembled in the ER/Golgi.","evidence":"SDS-PAGE oligomer characterization, TLR4 binding assays, and subcellular fractionation","pmids":["11593030"],"confidence":"Medium","gaps":["Functional significance of disulfide-linked oligomers unresolved","Single-lab biochemical characterization"]},{"year":2002,"claim":"Demonstrated genetically that MD-2 is essential in vivo for LPS responses and for delivering TLR4 to the plasma membrane.","evidence":"MD-2 knockout mice with LPS challenge plus fractionation/microscopy of fibroblasts showing Golgi retention of TLR4","pmids":["12055629"],"confidence":"High","gaps":["Molecular chaperone mechanism of TLR4 export not defined","Whether secreted vs membrane MD-2 drives trafficking unclear"]},{"year":2003,"claim":"Mapped MD-2 into two separable functional surfaces—one for TLR4 binding (Cys95-Cys105 disulfide region) and one for LPS responsiveness—and established that MD-2 must dock TLR4 before LPS-driven clustering.","evidence":"Site-directed mutagenesis with co-IP, LPS binding, confocal clustering and NF-κB reporter assays","pmids":["14607928","12960171","12642668"],"confidence":"High","gaps":["Conformational changes accompanying activation not visualized","Order of LPS loading vs TLR4 dimerization only inferred"]},{"year":2004,"claim":"Reconstituted the ordered LBP→CD14→MD-2 transfer pathway, explaining how the system achieves picomolar LPS sensitivity.","evidence":"Purified endotoxin–MD-2 complex, TLR4-dependent activation assay, and inhibition by excess soluble MD-2","pmids":["15010525"],"confidence":"High","gaps":["Kinetics of each transfer step not fully quantified","Structural intermediates of transfer not captured"]},{"year":2007,"claim":"Provided the structural foundation, revealing the MD-2 hydrophobic cavity that fully encloses lipid A acyl chains.","evidence":"X-ray crystallography of apo MD-2 and the lipid IVa complex","pmids":["17569869"],"confidence":"High","gaps":["Did not show how MD-2-bound LPS engages a second TLR4","Active receptor multimer not yet resolved"]},{"year":2009,"claim":"Resolved the active receptor architecture, showing LPS bridges two TLR4-MD-2 units into an m-shaped 2:2:2 complex via an exposed acyl chain and phosphate contacts.","evidence":"Crystal structure of the TLR4-MD-2-LPS complex plus mutagenesis of the hydrophobic dimerization interface (MD-2 V82/M85/L87, TLR4 F440/F463)","pmids":["19252480","19321453"],"confidence":"High","gaps":["Dynamics of dimerization in membranes not addressed","Link between clustering and downstream adaptor recruitment not structurally defined"]},{"year":2012,"claim":"Explained species-specific agonism/antagonism structurally, showing lipid IVa adopts opposite poses in mouse versus human MD-2.","evidence":"Crystal structures of mouse TLR4/MD-2 with LPS and with lipid IVa, complemented by combinatorial charge-reversal mutagenesis","pmids":["22532668","20592019","16407172","18606678"],"confidence":"High","gaps":["Full conformational switching mechanism in MD-2 not directly observed","Generalization to other partial lipid A structures incomplete"]},{"year":2016,"claim":"Established that the MD-2 pocket can be engaged by non-LPS chemotypes to drive canonical TLR4 signaling, validating it as a versatile and druggable ligand-binding module.","evidence":"Crystal structure of Neoseptin-3 bound to mouse MD-2 with MyD88/TRIF-KO and CD14-independence validation; pocket binding of paclitaxel, curcumin, opioids, sulfatides and inhibitors","pmids":["26831104","18650420","17609337","19679181","34290146"],"confidence":"High","gaps":["Endogenous physiological ligands beyond LPS incompletely catalogued","In vivo relevance of some pocket ligands uncertain"]},{"year":2020,"claim":"Extended MD-2 ligand repertoire to endogenous danger and acute-phase molecules (heme, SAA3, sCD83, Gb4), positioning MD-2 as a hub for sterile and endogenous TLR4 activation.","evidence":"Direct binding/pull-down, SPR, co-IP and mutagenesis with NF-κB readouts and KO mouse models","pmids":["32695117","23858030","28193829","23471986"],"confidence":"Medium","gaps":["Single-lab binding evidence for several ligands","Physiological concentrations and competition with LPS not resolved"]},{"year":2023,"claim":"Demonstrated therapeutic targeting of MD-2, with covalent Cys133 modification blocking TLR4 dimerization and reducing inflammation in disease models.","evidence":"Disulfiram covalent modification of Cys133, dimerization/reporter assays, macrophage cytokine assays and an MPTP Parkinson's mouse model","pmids":["37487070","26076332"],"confidence":"High","gaps":["Selectivity of covalent inhibitors for MD-2 in vivo not fully established","Translation to human disease unproven"]},{"year":null,"claim":"How MD-2 conformational switching couples ligand binding within the pocket to productive TLR4 dimerization and adaptor recruitment, and how the diverse endogenous ligands are physiologically prioritized, remain incompletely defined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No time-resolved structural view of pocket-to-dimerization signal transmission","Competition hierarchy among endogenous MD-2 ligands unresolved","Mechanism by which secreted MD-2 chaperones TLR4 export not molecularly defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[2,4,5]},{"term_id":"GO:0001618","term_label":"virus receptor activity","supporting_discovery_ids":[0,2]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,5]},{"term_id":"GO:0038024","term_label":"cargo receptor activity","supporting_discovery_ids":[38,39]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1,16]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[1,8,16]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[38,39]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[8]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,1,5]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,5,20]}],"complexes":["TLR4-MD-2 LPS receptor complex","TLR4-MD-2-LPS 2:2:2 signaling complex","LBP-CD14-MD-2 endotoxin transfer system"],"partners":["TLR4","CD14","LBP","TLR2","SAA3","CD83","PTX3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9Y6Y9","full_name":"Lymphocyte antigen 96","aliases":["ESOP-1","Protein MD-2"],"length_aa":160,"mass_kda":18.5,"function":"Binds bacterial lipopolysaccharide (LPS) (PubMed:17569869, PubMed:17803912). Cooperates with TLR4 in the innate immune response to bacterial lipopolysaccharide (LPS), and with TLR2 in the response to cell wall components from Gram-positive and Gram-negative bacteria (PubMed:11160242, PubMed:11593030). Enhances TLR4-dependent activation of NF-kappa-B (PubMed:10359581). Cells expressing both LY96 and TLR4, but not TLR4 alone, respond to LPS (PubMed:10359581)","subcellular_location":"Secreted, extracellular space; Secreted","url":"https://www.uniprot.org/uniprotkb/Q9Y6Y9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/LY96","classification":"Not Classified","n_dependent_lines":6,"n_total_lines":1208,"dependency_fraction":0.004966887417218543},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/LY96","total_profiled":1310},"omim":[{"mim_id":"619990","title":"TRANSMEMBRANE p24 TRAFFICKING PROTEIN 7; TMED7","url":"https://www.omim.org/entry/619990"},{"mim_id":"605243","title":"LYMPHOCYTE ANTIGEN 96; LY96","url":"https://www.omim.org/entry/605243"},{"mim_id":"603030","title":"TOLL-LIKE RECEPTOR 4; TLR4","url":"https://www.omim.org/entry/603030"},{"mim_id":"187380","title":"TENASCIN C; TNC","url":"https://www.omim.org/entry/187380"},{"mim_id":"123886","title":"S100 CALCIUM-BINDING PROTEIN A9; S100A9","url":"https://www.omim.org/entry/123886"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"lymphoid tissue","ntpm":61.4}],"url":"https://www.proteinatlas.org/search/LY96"},"hgnc":{"alias_symbol":["MD-2"],"prev_symbol":[]},"alphafold":{"accession":"Q9Y6Y9","domains":[{"cath_id":"2.60.40.770","chopping":"29-156","consensus_level":"medium","plddt":92.4318,"start":29,"end":156}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y6Y9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y6Y9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y6Y9-F1-predicted_aligned_error_v6.png","plddt_mean":87.69},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=LY96","jax_strain_url":"https://www.jax.org/strain/search?query=LY96"},"sequence":{"accession":"Q9Y6Y9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y6Y9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y6Y9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y6Y9"}},"corpus_meta":[{"pmid":"19252480","id":"PMC_19252480","title":"The structural basis of lipopolysaccharide 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in MD-2-deficient fibroblasts, TLR4 fails to reach the plasma membrane and is retained in the Golgi apparatus, demonstrating that MD-2 is essential for correct intracellular trafficking and plasma membrane localization of TLR4.\",\n      \"method\": \"MD-2 knockout mouse (in vivo LPS challenge, Salmonella infection); subcellular fractionation and microscopy of embryonic fibroblasts\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout with defined in vivo phenotype plus direct localization experiment; independently confirmed across multiple studies\",\n      \"pmids\": [\"12055629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"MD-2 directly binds LPS (apparent KD ~65 nM) independently of LBP and CD14; LBP competes with MD-2 for LPS binding, establishing MD-2 as a genuine LPS-binding protein.\",\n      \"method\": \"Recombinant protein production, five independent binding assays (including equilibrium binding with Kd determination); competition assay with LBP\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct in vitro binding assay with recombinant protein and Kd measurement, multiple orthogonal binding assays in one study\",\n      \"pmids\": [\"11500507\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"LPS is cross-linked directly to both TLR4 and MD-2 (and CD14) when co-expressed with CD14, demonstrating LPS is in close proximity to each member of the tripartite receptor complex; CD14 is required for LPS transfer to TLR4 and MD-2.\",\n      \"method\": \"Radioiodinated photoactivatable LPS cross-linking assay in transiently transfected HEK293 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct covalent photocrosslinking with radiolabeled LPS, chemical crosslinking with functional validation, single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"11274165\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Crystal structure of human MD-2 (2.0 Å) reveals a deep hydrophobic cavity formed by two beta-sheets; in complex with tetra-acylated lipid IVa, all four acyl chains are fully enclosed in this cavity with the phosphorylated glucosamine moieties at the cavity entrance, establishing MD-2 as the principal endotoxin-binding subunit.\",\n      \"method\": \"X-ray crystallography at 2.0 Å (apo MD-2) and 2.2 Å (lipid IVa complex)\",\n      \"journal\": \"Science (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structures of both apo and ligand-bound forms; foundational structural paper replicated by subsequent structures\",\n      \"pmids\": [\"17569869\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Crystal structure of the TLR4-MD-2-LPS complex at ~3 Å resolution reveals an m-shaped 2:2:2 receptor multimer; five of six LPS lipid chains are buried in MD-2's hydrophobic pocket while the sixth is exposed and contacts conserved TLR4 phenylalanines; LPS directly bridges two TLR4-MD-2 units; the MD-2 F126 loop undergoes localized conformational change to support TLR4 dimerization; phosphate groups of LPS form ionic interactions with positively charged residues in TLR4 and MD-2 to stabilize the active complex.\",\n      \"method\": \"X-ray crystallography of TLR4-MD-2-LPS complex\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — landmark crystal structure of full receptor complex, independently confirmed by subsequent mouse TLR4/MD-2/LPS structure\",\n      \"pmids\": [\"19252480\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Purified monomeric endotoxin-MD-2 complex (generated by sequential transfer from LBP→sCD14→MD-2) activates TLR4-expressing cells at picomolar endotoxin concentrations; excess free MD-2 inhibits delivery of the endotoxin-MD-2 complex to TLR4 cells, establishing ordered sequential transfer as the mechanism for high-sensitivity LPS detection.\",\n      \"method\": \"Purification of recombinant endotoxin-MD-2 complex; TLR4-dependent cell activation assay; inhibition studies with excess soluble MD-2\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — biochemical reconstitution with purified components, functional validation in cell assay with competition controls, single lab with multiple orthogonal approaches\",\n      \"pmids\": [\"15010525\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Cell surface LPS-TLR4-MD-2 complexes form with a Kd ~3 nM; CD14 greatly enhances LPS loading onto TLR4-MD-2 but is not retained in the final complex; detergent disrupts LPS-CD14 but not LPS-TLR4-MD-2 interaction.\",\n      \"method\": \"Co-immunoprecipitation of LPS-TLR4-MD-2 complexes from cell surface; competition binding with lipid A antagonist E5531; Kd estimation\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding measurement with Kd, reciprocal precipitation, and pharmacological competition; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"14517279\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"MD-2 exists predominantly as large disulfide-linked oligomers in solution; monomeric MD-2 preferentially binds TLR4 and confers LPS responsiveness more efficiently than multimeric forms; MD-2 associates with TLR4 in the ER/cis-Golgi before being secreted.\",\n      \"method\": \"Secreted MD-2 characterization by SDS-PAGE, TLR4 binding assays; LPS responsiveness reporter assay; subcellular fractionation\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical characterization with multiple methods (SDS-PAGE, functional assays, fractionation) in a single lab study\",\n      \"pmids\": [\"11593030\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"N-linked glycosylation at Asn26 and Asn114 of MD-2 is not required for cell surface expression, but the double glycosylation mutant of MD-2 fails to support LPS-induced NF-κB activation, IL-8 secretion, or JNK activation, demonstrating that N-linked carbohydrates of MD-2 are essential for functional LPS receptor integrity.\",\n      \"method\": \"Site-directed mutagenesis of N-glycosylation sites; UV-crosslinking LPS binding assay; NF-κB/IL-8/JNK activation assays in transfected HeLa cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — site-directed mutagenesis combined with multiple functional readouts (crosslinking, reporter, cytokine, kinase) in single study\",\n      \"pmids\": [\"11706042\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Lysines 128 and 132 of MD-2 are required for LPS binding; MD-2 must be surface-bound to TLR4 before LPS binding and TLR4 receptor cluster formation can occur; CD14 enhances LPS binding to MD-2 but is not essential for cellular activation.\",\n      \"method\": \"Site-directed mutagenesis; LPS binding assay; confocal microscopy of TLR4 clustering; NF-κB reporter assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — mutagenesis with direct LPS-binding assay and visual receptor clustering readout, multiple orthogonal methods in single study\",\n      \"pmids\": [\"12960171\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Separate domains of human MD-2 mediate TLR4 binding and LPS responsiveness; Cys95 and Cys105 (forming an intramolecular disulfide) and surrounding residues (R90, K91, D100, Y102) are required for TLR4 binding; a distinct basic/aromatic region is responsible for conferring LPS responsiveness.\",\n      \"method\": \"Site-directed mutagenesis; co-immunoprecipitation; NF-κB reporter assay; dominant-negative inhibition in primary endothelial cells\",\n      \"journal\": \"Journal of immunology (Baltimore, Md. : 1950)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — systematic mutagenesis mapping two distinct functional domains with both binding and signaling readouts\",\n      \"pmids\": [\"14607928\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The intramolecular disulfide bond between Cys95 and Cys105 of MD-2 is essential for LPS responsiveness; substitution of either Cys95 or Cys105 alone abolishes activity, whereas simultaneous substitution of both partially restores it; most Cys residues can participate in intermolecular oligomer formation.\",\n      \"method\": \"17 single and multiple Cys-to-Ser substitution mutants analyzed by SDS-PAGE and NF-κB reporter assay; structural analysis of disulfide connectivity\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — systematic mutagenesis of all seven Cys residues with structural and functional characterization in single study\",\n      \"pmids\": [\"12642668\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Human MD-2 determines species-specific LPS recognition: hMD-2 confers responsiveness to lipid A but not to lipid IVa when associated with mouse TLR4, whereas mouse MD-2 confers responsiveness to both, demonstrating that MD-2 directly controls the fine ligand specificity of TLR4.\",\n      \"method\": \"Chimeric receptor (mTLR4/hMD-2) transfection and NF-κB activation assay; pharmacological analysis with lipid IVa as agonist/antagonist probe\",\n      \"journal\": \"International immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — species-chimeric receptor approach with clear mechanistic conclusion; replicated by subsequent crystal structures and mutagenesis studies\",\n      \"pmids\": [\"11717200\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Co-expression of mouse TLR4 and mouse MD-2 is required for Taxol-induced NF-κB signaling; human TLR4/hMD-2 does not confer Taxol responsiveness; an LPS antagonist also blocks Taxol-induced signaling via TLR4/MD-2, indicating TLR4/MD-2 is the shared signaling complex for both Taxol and LPS in mice and that species specificity resides in MD-2.\",\n      \"method\": \"Ba/F3 transfectants expressing species-specific TLR4/MD-2 combinations; NF-κB reporter assay; pharmacological blockade\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean transfection model with species chimeras, pharmacological validation, replicated in a follow-up study (PMID 11581576)\",\n      \"pmids\": [\"10644670\", \"11581576\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Paclitaxel binds directly to recombinant human MD-2 protein (dose-dependent, blocked by anti-MD-2 antibody); murine MD-2, not human MD-2, is required for TLR4 activation by paclitaxel; species-specific differences in pocket size, surface charge, and position of binding within the MD-2 pocket — particularly involving Phe126 as a dimerization bridge — explain species specificity.\",\n      \"method\": \"ELISA-based binding assay with recombinant hMD-2; HEK293 transfections with human/murine TLR4/MD-2 chimeras; computational docking to crystal structures\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding assay with antibody inhibition plus chimeric receptor functional study; computational docking is supportive but not definitive\",\n      \"pmids\": [\"18650420\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"TLR4-CD14-MD-2 complexes rapidly and constitutively recycle between the plasma membrane and the Golgi apparatus; LPS follows these trafficking pathways in CD14-positive cells; MyD88 translocates to the cell surface upon LPS exposure; Golgi-localized TLR4 is not required for LPS signaling (brefeldin A disrupts Golgi TLR4 but preserves signaling).\",\n      \"method\": \"Fluorescent TLR4 live-cell confocal imaging; brefeldin A treatment; MyD88 translocation assay; cross-linking-induced signaling\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct live-cell imaging with pharmacological dissection; multiple orthogonal approaches in single study\",\n      \"pmids\": [\"12324469\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"MD-2 residues Phe126 and Gly129 are required for LPS-induced TLR4 receptor clustering but not for LPS binding; Gly59 is a novel critical residue for LPS binding; receptor clustering and LPS-receptor dissociation depend on TLR4 signaling and require endosomal acidification.\",\n      \"method\": \"MD-2 alanine-scanning mutagenesis; LPS binding assay; TLR4 clustering assay by microscopy; pharmacological blockade of endosomal acidification\",\n      \"journal\": \"Journal of immunology (Baltimore, Md. : 1950)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — systematic mutagenesis dissecting binding from clustering with multiple orthogonal readouts\",\n      \"pmids\": [\"16670331\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Hydrophobic residues Val82, Met85, and Leu87 in the MD-2 hairpin loop (β5–β6) are essential for transfer of endotoxin from CD14 to monomeric MD-2 and for TLR4 activation; conserved hydrophobic residues Phe440 and Phe463 in TLR4 LRR16–17 are also essential for activation; these residues form a hydrophobic interface between the exposed acyl chain of LPS-bound MD-2 and the neighboring TLR4.\",\n      \"method\": \"Site-directed mutagenesis of MD-2 and TLR4; endotoxin transfer assay from CD14 to MD-2; NF-κB reporter assay in transfected cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — systematic mutagenesis of both MD-2 and TLR4 with defined biochemical transfer assay plus signaling readout; consistent with crystal structure\",\n      \"pmids\": [\"19321453\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Crystal structures of mouse TLR4/MD-2/LPS (2.5 Å) and TLR4/MD-2/lipid IVa (2.7 Å) complexes show that lipid IVa in mouse MD-2 occupies nearly the same space as LPS and induces an agonistic 2:2:2 complex similar to LPS; human MD-2 binds lipid IVa in a completely different, antagonistic manner, providing structural basis for species-specific agonism/antagonism.\",\n      \"method\": \"X-ray crystallography of mouse TLR4/MD-2/LPS and TLR4/MD-2/lipid IVa complexes\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structures of both agonist and antagonist complexes in the same study, consistent with prior human structures\",\n      \"pmids\": [\"22532668\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Neoseptin-3, a peptidomimetic with no structural similarity to LPS, activates mouse TLR4/MD-2 by binding as an asymmetrical dimer within the MD-2 hydrophobic pocket; crystal structure at 2.57 Å shows an active 2:2 receptor complex similar to lipid A; activation is CD14-independent and triggers canonical MyD88- and TRIF-dependent signaling.\",\n      \"method\": \"X-ray crystallography at 2.57 Å; NF-κB/IRF3 reporter assays; MyD88/TRIF knockout validation; CD14-independence experiments\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus genetic validation with knockout cells and multiple signaling pathway readouts\",\n      \"pmids\": [\"26831104\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Short-chain sulfatides directly bind the MD-2 hydrophobic pocket and activate mouse TLR4-MD-2 (MyD88- and TRIF-dependent) independently of CD14; crystal structure of mouse TLR4-MD-2/C16-sulfatide at 2.6 Å shows three sulfatide molecules in the MD-2 pocket inducing an active 2:2 complex; sulfatides antagonize human TLR4-MD-2, with agonism/antagonism dependent on the sulfate group and inversely related to FA chain length.\",\n      \"method\": \"Crystal structure; macrophage activation assays; MyD88/TRIF-knockout validation; structure-activity relationship with sulfatide variants\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure of endogenous lipid-MD-2 complex combined with genetic (KO) and pharmacological validation\",\n      \"pmids\": [\"34290146\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Curcumin binds MD-2 at submicromolar affinity in its hydrophobic pocket (fluorescence blue-shift assay); the binding site overlaps with LPS; curcumin inhibits both MyD88-dependent and -independent TLR4 signaling; C133F mutant MD-2 retains curcumin binding, and curcumin does not form a covalent bond to the free thiol of MD-2.\",\n      \"method\": \"Fluorescence spectroscopy; competition binding with LPS; NF-κB reporter assay; C133F mutagenesis\",\n      \"journal\": \"Journal of leukocyte biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding assay with spectroscopic evidence plus functional mutagenesis, single lab\",\n      \"pmids\": [\"17609337\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Disulfiram (DSF) covalently modifies Cys133 of MD-2, blocking LPS-induced TLR4 dimerization, cell surface expression, and downstream NF-κB/IRF3 signaling; this mechanism suppresses inflammatory cytokine/interferon production by macrophages in vitro and reduces neuroinflammation and dopaminergic neuron loss in an MPTP mouse model of Parkinson's disease.\",\n      \"method\": \"Covalent modification identification; TLR4 dimerization assay; NF-κB/IRF3 reporter; macrophage cytokine assay; MPTP mouse model in vivo\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — covalent modification of defined residue with multiple orthogonal functional assays (in vitro and in vivo), single study\",\n      \"pmids\": [\"37487070\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Structural model of MD-2 (based on NPC2/Der p2 homology) predicted a beta-sandwich hydrophobic pocket; two basic residue clusters (Lys89-Arg90-Lys91 and Lys125-Lys132) are required for LPS signal transduction upon co-expression with TLR4 or as soluble protein added to TLR4-expressing cells; a peptide spanning the Cys95-Cys105 loop inhibited LPS-induced TNF-α and IL-8 production.\",\n      \"method\": \"Homology modeling; CD spectroscopy (confirming beta-sheet content); site-directed mutagenesis; NF-κB reporter assay; TNF-α/IL-8 inhibition with synthetic peptide\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis with functional validation plus peptide inhibition, but structural model is computational; corroborated by later crystal structures\",\n      \"pmids\": [\"15111623\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"MD-2 physically associates with TLR2 (in addition to TLR4), enabling TLR2 to respond to LPS and lipid A structures that are otherwise non-activating; the MD-2-TLR2 interaction is weaker than the MD-2-TLR4 interaction; MD-2 enhances expression of both TLR2 and TLR4.\",\n      \"method\": \"Co-immunoprecipitation; NF-κB reporter assays in transfected cells; flow cytometry for surface expression\",\n      \"journal\": \"Journal of immunology (Baltimore, Md. : 1950)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP demonstrating physical association plus functional transfection assays, single lab study\",\n      \"pmids\": [\"11160242\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Structural regions 57-79 and 108-135 of MD-2 determine the agonist-antagonist activity of lipid IVa; single amino acid substitutions at Thr57, Val61, and Glu122 in mouse MD-2 impair lipid IVa agonism while preserving LPS (E. coli lipid A) activation.\",\n      \"method\": \"Human/mouse chimeric MD-2 expression; NF-κB reporter assay in HEK293 cells; point mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic chimeric and point mutagenesis with clear functional readout, single lab\",\n      \"pmids\": [\"16407172\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"MD-2 residues Tyr42, Arg69, Asp122, and Leu125 determine lipid IVa species specificity; E122K mutation in mouse MD-2 substantially reduces lipid IVa response; combining MD-2 and TLR4 charge-reversal mutations can completely convert murine receptor response to a human-like pattern (and vice versa), demonstrating that MD-2 surface charges at two distinct interfaces (pocket entrance and MD-2/TLR4 contact surface) govern species-specific activation.\",\n      \"method\": \"Site-directed mutagenesis; stable TLR4-expressing cell lines; purified monomeric MD-2; MD-2-deficient bone marrow macrophages; NF-κB reporter assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — systematic combinatorial mutagenesis of both MD-2 and TLR4 with primary cell validation, single study with multiple orthogonal approaches\",\n      \"pmids\": [\"20592019\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Morphine and structurally diverse opioids activate TLR4 signaling non-stereoselectively; in silico docking indicates opioids bind preferentially to the LPS-binding pocket of MD-2 rather than TLR4; naloxone blocks this signaling non-stereoselectively; TLR4 knockout mice show a threefold leftward shift in morphine analgesia dose-response.\",\n      \"method\": \"In vitro TLR4 reporter assay; pharmacological blockade (naloxone, classical TLR4 antagonist); TLR4 knockout mouse; in silico docking to MD-2 pocket\",\n      \"journal\": \"Brain, behavior, and immunity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro functional assay plus knockout mouse validation; docking is computational and supportive only; single lab\",\n      \"pmids\": [\"19679181\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Serum amyloid A3 (SAA3) synthetic peptide (aa 20-86) directly binds MD-2 (not TLR4) with KD ~2.2 μM as measured by surface plasmon resonance; FLAG-tagged SAA3 co-precipitates with protein A-tagged MD-2 in baculovirus co-infection experiments; SAA3-MD-2 interaction activates MyD88-dependent TLR4 signaling (p38, NF-κB, Rho GTPase) but not TRIF-dependent IFN-β.\",\n      \"method\": \"Surface plasmon resonance; co-immunoprecipitation in baculovirus system; NF-κB/p38 activation assays; TLR4/MyD88 KO validation\",\n      \"journal\": \"Journal of immunology (Baltimore, Md. : 1950)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — direct binding measurement (SPR with KD) plus co-IP and genetic (KO) validation in single study\",\n      \"pmids\": [\"23858030\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Soluble CD83 (sCD83) binds MD-2 as a high-affinity partner; sCD83 binding to MD-2 on monocytes rapidly degrades IRAK-1 and induces anti-inflammatory mediators (IDO, IL-10, PGE2 via COX-2), leading to T cell unresponsiveness.\",\n      \"method\": \"Pull-down/co-IP identifying MD-2 as sCD83 binding partner; IRAK-1 degradation assay; IDO/IL-10/PGE2 measurement; T cell proliferation assay\",\n      \"journal\": \"Journal of immunology (Baltimore, Md. : 1950)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — binding partner identification plus functional signaling characterization, single lab study\",\n      \"pmids\": [\"28193829\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PTX3 directly binds MD-2 in vitro; in MD-2-knockout mice, PTX3 fails to confer immune protection against Aspergillus fumigatus; MD-2-competent PMN adoptive transfer restores protection; PTX3-opsonized conidia activate TLR4/MD-2/TRIF-dependent signaling converging on IL-10.\",\n      \"method\": \"In vitro binding assay (PTX3-MD-2); MD-2 knockout mouse model; adoptive transfer of MD-2-competent PMN; cytokine profiling\",\n      \"journal\": \"Journal of immunology (Baltimore, Md. : 1950)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro binding plus genetic (KO) and adoptive transfer in vivo validation; single lab\",\n      \"pmids\": [\"25049357\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Globotetraosylceramide (Gb4) binds to TLR4-MD-2 (co-precipitated with recombinant MD-2; confirmed by native PAGE and docking); Gb4 competes with LPS for TLR4-MD-2 binding; A4galt-deficient mice lacking Gb4 show increased LPS sensitivity; exogenous Gb4 protects mice from LPS-induced mortality.\",\n      \"method\": \"Co-precipitation of Gb4 with recombinant MD-2; native PAGE; A4galt-knockout mouse; in vivo LPS challenge; gene expression assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding demonstrated biochemically plus KO mouse model; docking is computational; single lab\",\n      \"pmids\": [\"23471986\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Heme binds MD-2 and activates TLR4 signaling; MD-2 is required for heme-mediated NF-κB activation (absent without MD-2); heme binding site involves residues W23 and Y34 (mutagenesis reduces heme pull-down and NF-κB response); site Y36A increases heme-induced NF-κB signaling without affecting LPS response.\",\n      \"method\": \"Heme-agarose/biotin-heme pull-down of recombinant MD-2; UV/visible spectroscopy; site-directed mutagenesis; NF-κB luciferase reporter in HEK293; in silico docking\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — direct binding assays plus mutagenesis identifying binding residues, with multiple orthogonal methods; single lab study\",\n      \"pmids\": [\"32695117\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Monomeric recombinant MD-2 can interact with the soluble extracellular domain of TLR4 in solution; MD-2's ability to confer LPS responsiveness and to bind TLR4 are strongly associated; more than two intermolecular disulfide bonds stabilize MD-2 multimers.\",\n      \"method\": \"Biochemical binding assay (TLR4 ectodomain-MD-2 interaction in solution); site-directed mutagenesis of Cys residues; NF-κB reporter assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding assay with recombinant proteins plus mutagenesis, single lab\",\n      \"pmids\": [\"11976338\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Intracellular TLR4/MD-2 (present in the absence of cell-surface TLR4) can sense phagocytosed gram-negative bacteria and activate MyD88-dependent chemokine production (CCL2, CCL5) and co-stimulatory molecule upregulation (CD40, CD86) independently of TRIF/TICAM-1; intracellular TLR4/MD-2 requires PRAT4A-independent compartment; TRIF-dependent type I IFN production depends on surface TLR4.\",\n      \"method\": \"PRAT4A knockout macrophages (abolishing surface TLR4); intracellular LPS sensing assay; cytokine/chemokine measurement; co-stimulatory molecule flow cytometry\",\n      \"journal\": \"International immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO model with specific intracellular sensing readouts; single lab study\",\n      \"pmids\": [\"21712422\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"MD-2 expression in intestinal epithelial cells (IECs) is regulated epigenetically; IFN-γ positively regulates the MD-2 promoter through JAK-STAT signaling (blocked by STAT inhibitor SOCS3); IFN-γ and TNF-α sensitize IECs to LPS-dependent IL-8 secretion by upregulating MD-2.\",\n      \"method\": \"RT-PCR; Western blot; MD-2 promoter reporter assay; SOCS3 overexpression; IL-8 secretion assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — promoter-reporter assay with SOCS3 dominant-negative, multiple functional readouts; single lab\",\n      \"pmids\": [\"11923281\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Epigenetic silencing (CpG methylation and histone deacetylation) of the MD-2 promoter underlies low MD-2 expression and LPS unresponsiveness in intestinal epithelial cells; inhibition of methylation (5-azacytidine) or histone deacetylation (trichostatin A) increases MD-2 mRNA expression; LPS responsiveness is polarized to the basolateral membrane of IECs.\",\n      \"method\": \"Bisulfite sequencing of MD-2 promoter; 5-azacytidine and trichostatin A treatment; MD-2 mRNA quantification; NF-κB reporter assay\",\n      \"journal\": \"Innate immunity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct bisulfite sequencing of promoter CpG methylation plus pharmacological reversal; single lab\",\n      \"pmids\": [\"19710105\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Soluble MD-2 is a type II acute-phase protein: mRNA and protein levels rise in mouse liver during acute-phase response; IL-6 upregulates sMD-2 secretion from hepatocytes; sMD-2 binds gram-negative (but not gram-positive) bacteria and functions as an opsonin, enhancing phagocytosis by neutrophils and serving as a cofactor for TLR4-expressing cell activation by gram-negative bacteria.\",\n      \"method\": \"Mouse acute-phase response model; IL-6 stimulation of hepatocytes; bacterial binding assay; phagocytosis assay; TLR4-dependent cell activation assay\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal assays (in vivo model, cell assay, phagocytosis, bacterial binding) in single study; single lab\",\n      \"pmids\": [\"18056837\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Soluble MD-2 binds to the surface of live gram-negative bacteria; MD-2-coated bacteria show enhanced cellular activation, bacterial internalization, and intracellular killing, all in a TLR4-signaling-dependent manner (absent in Lpsd macrophages with signaling-deficient TLR4), confirming sMD-2 as an opsonin that bridges bacteria to TLR4.\",\n      \"method\": \"MD-2 binding to live bacteria (binding assay); phagocytosis/killing assays in WT vs. Lpsd macrophages; TLR4-dependence controls\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional opsonophagocytosis assay with signaling-incompetent TLR4 control; single lab\",\n      \"pmids\": [\"18203953\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The chalcone derivative L6H21 inserts into the hydrophobic pocket of MD-2, forming hydrogen bonds with Arg90 and Tyr102; it suppresses LPS-induced TLR4/MD-2 complex formation and downstream MAPK/NF-κB signaling; MD-2 knockout mice are universally protected from LPS-induced septic shock, validating MD-2 as the essential therapeutic target.\",\n      \"method\": \"SPR binding assay; ELISA; fluorescence measurement; flow cytometry; computer docking; Western blot/EMSA; MD-2 knockout mouse model\",\n      \"journal\": \"British journal of pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding with SPR plus KO mouse validation and multiple signaling readouts; single lab\",\n      \"pmids\": [\"26076332\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Zebrafish possess an MD-2 ortholog encoded by the ly96 gene; zebrafish Md-2 and Tlr4ba form a functional complex that activates NF-κB signaling in response to LPS; ly96 loss-of-function in larval zebrafish perturbs LPS-induced cytokine production, establishing an ancestral Tlr4/Md-2 LPS-sensing complex in teleosts.\",\n      \"method\": \"Bioinformatic identification; single-cell RNA sequencing; functional NF-κB reporter assay with zebrafish Md-2/Tlr4ba co-expression; ly96 loss-of-function mutation analysis\",\n      \"journal\": \"Journal of immunology (Baltimore, Md. : 1950)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional reconstitution assay plus loss-of-function genetics; single lab study on zebrafish ortholog\",\n      \"pmids\": [\"33472906\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"MD-2 residues 57-66 and 82-89 (horse vs. human) and a single residue in the glycan-free flank of TLR4 solenoid determine whether lipid IVa acts as agonist or antagonist; replacing horse MD-2 residues 57-66 and 82-89 with human equivalents confers constitutive activity, suggesting conformational switching in MD-2 is important for ligand-induced activation.\",\n      \"method\": \"Horse/human chimeric MD-2 and TLR4 constructs; NF-κB reporter assay; surface charge analysis\",\n      \"journal\": \"Journal of immunology (Baltimore, Md. : 1950)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — chimeric and point-mutant receptor approach with functional signaling readout; single lab\",\n      \"pmids\": [\"18606678\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"A single coding mutation in human MD-2 (Thr35Ala, A→G at position 103) results in reduced LPS-induced signaling in reporter gene assays, demonstrating that Thr35 contributes to MD-2 function.\",\n      \"method\": \"SSCP mutation screening; Lightcycler/FRET genotyping; NF-κB reporter gene assay; in vitro LPS stimulation (TNF-α measurement)\",\n      \"journal\": \"Genes and immunity\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single patient-derived mutant with reporter assay; no structural or binding characterization; single lab\",\n      \"pmids\": [\"15057266\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MD-2 (LY96) is a secreted beta-sandwich glycoprotein that constitutively associates with the extracellular domain of TLR4 in the ER/Golgi, enabling TLR4 trafficking to the plasma membrane and forming the essential co-receptor for LPS recognition; LPS is transferred sequentially from LBP→CD14→MD-2, binds deeply within MD-2's hydrophobic pocket (up to five of six acyl chains buried), and the resulting LPS-MD-2 complex bridges two TLR4-MD-2 heterodimers into an active m-shaped 2:2:2 signaling complex through hydrophobic contacts between the exposed LPS acyl chain and conserved TLR4 phenylalanines (Phe440/Phe463) and ionic interactions between LPS phosphates and charged residues at the dimerization interface; distinct MD-2 surface regions mediate TLR4 binding (Cys95-Cys105 disulfide loop) versus LPS binding and receptor activation (hydrophobic pocket residues, F119/F121, K128/K132, F126/G129 for clustering), and species-specific differences in MD-2 surface charges and pocket geometry determine whether partial lipid A structures act as agonists or antagonists; beyond LPS, MD-2 serves as a direct binding site for endogenous ligands (sulfatides, Gb4, heme, SAA3, sCD83, S100A8), opioids, paclitaxel, and pharmacological inhibitors, and soluble MD-2 functions as an acute-phase opsonin for gram-negative bacteria.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MD-2 (LY96) is the essential LPS-binding co-receptor of the innate immune endotoxin sensor, a secreted β-sandwich glycoprotein that constitutively associates with the extracellular domain of TLR4 and renders TLR4-expressing cells responsive to LPS [#0]. MD-2 is required for TLR4 to exit the Golgi and reach the plasma membrane, and genetic loss of MD-2 abolishes LPS responses and protects mice from endotoxic shock [#1, #40]. MD-2 binds LPS directly with nanomolar affinity, independently of LBP and CD14, and is the principal endotoxin-binding subunit of the receptor [#2], its crystal structure revealing a deep hydrophobic cavity that buries the acyl chains of lipid A while presenting the phosphorylated glucosamine head groups at the cavity rim [#4]. High-sensitivity detection proceeds by ordered, sequential transfer of endotoxin from LBP to CD14 to MD-2, producing a monomeric endotoxin–MD-2 complex that activates TLR4 at picomolar concentrations [#6]. In the assembled TLR4–MD-2–LPS structure, five of six LPS acyl chains are enclosed in the MD-2 pocket while the exposed sixth chain and LPS phosphates bridge a second TLR4–MD-2 unit, building the active m-shaped 2:2:2 signaling complex [#5, #18]. Functionally distinct MD-2 surfaces separate TLR4 binding (the Cys95–Cys105 disulfide loop) from LPS binding and receptor clustering (hydrophobic pocket residues and the F126/G129 region), and species-specific differences in MD-2 pocket geometry and surface charge dictate whether partial lipid A structures such as lipid IVa act as agonists or antagonists [#11, #17, #19, #27]. Beyond LPS, the MD-2 pocket accommodates diverse exogenous and endogenous ligands—paclitaxel, sulfatides, Gb4, heme, SAA3, sCD83—and small-molecule inhibitors targeting the pocket or covalently modifying Cys133 block TLR4 activation, establishing MD-2 as a tractable anti-inflammatory drug target [#15, #21, #23, #29]. Soluble MD-2 additionally functions as an acute-phase opsonin that coats gram-negative bacteria and promotes their TLR4-dependent phagocytosis and killing [#38, #39].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Established that TLR4 alone is insufficient for LPS sensing and that a physically associated partner, MD-2, is required—defining the existence of a co-receptor.\",\n      \"evidence\": \"Co-immunoprecipitation and MD-2 transfection conferring LPS responsiveness via NF-κB reporter\",\n      \"pmids\": [\"10359581\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve whether MD-2 binds LPS directly or only stabilizes TLR4\", \"No structural detail of the interaction\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Showed MD-2 is itself a genuine LPS-binding protein, localizing endotoxin recognition to MD-2 rather than TLR4.\",\n      \"evidence\": \"Recombinant MD-2 binding assays with Kd determination and LBP competition\",\n      \"pmids\": [\"11500507\", \"11274165\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the binding pocket not yet known\", \"Stoichiometry within the activated receptor undefined\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined MD-2 quaternary state and its trafficking origin, showing monomeric MD-2 is the functional TLR4-binding species assembled in the ER/Golgi.\",\n      \"evidence\": \"SDS-PAGE oligomer characterization, TLR4 binding assays, and subcellular fractionation\",\n      \"pmids\": [\"11593030\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional significance of disulfide-linked oligomers unresolved\", \"Single-lab biochemical characterization\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Demonstrated genetically that MD-2 is essential in vivo for LPS responses and for delivering TLR4 to the plasma membrane.\",\n      \"evidence\": \"MD-2 knockout mice with LPS challenge plus fractionation/microscopy of fibroblasts showing Golgi retention of TLR4\",\n      \"pmids\": [\"12055629\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular chaperone mechanism of TLR4 export not defined\", \"Whether secreted vs membrane MD-2 drives trafficking unclear\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Mapped MD-2 into two separable functional surfaces—one for TLR4 binding (Cys95-Cys105 disulfide region) and one for LPS responsiveness—and established that MD-2 must dock TLR4 before LPS-driven clustering.\",\n      \"evidence\": \"Site-directed mutagenesis with co-IP, LPS binding, confocal clustering and NF-κB reporter assays\",\n      \"pmids\": [\"14607928\", \"12960171\", \"12642668\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Conformational changes accompanying activation not visualized\", \"Order of LPS loading vs TLR4 dimerization only inferred\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Reconstituted the ordered LBP→CD14→MD-2 transfer pathway, explaining how the system achieves picomolar LPS sensitivity.\",\n      \"evidence\": \"Purified endotoxin–MD-2 complex, TLR4-dependent activation assay, and inhibition by excess soluble MD-2\",\n      \"pmids\": [\"15010525\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinetics of each transfer step not fully quantified\", \"Structural intermediates of transfer not captured\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Provided the structural foundation, revealing the MD-2 hydrophobic cavity that fully encloses lipid A acyl chains.\",\n      \"evidence\": \"X-ray crystallography of apo MD-2 and the lipid IVa complex\",\n      \"pmids\": [\"17569869\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not show how MD-2-bound LPS engages a second TLR4\", \"Active receptor multimer not yet resolved\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Resolved the active receptor architecture, showing LPS bridges two TLR4-MD-2 units into an m-shaped 2:2:2 complex via an exposed acyl chain and phosphate contacts.\",\n      \"evidence\": \"Crystal structure of the TLR4-MD-2-LPS complex plus mutagenesis of the hydrophobic dimerization interface (MD-2 V82/M85/L87, TLR4 F440/F463)\",\n      \"pmids\": [\"19252480\", \"19321453\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Dynamics of dimerization in membranes not addressed\", \"Link between clustering and downstream adaptor recruitment not structurally defined\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Explained species-specific agonism/antagonism structurally, showing lipid IVa adopts opposite poses in mouse versus human MD-2.\",\n      \"evidence\": \"Crystal structures of mouse TLR4/MD-2 with LPS and with lipid IVa, complemented by combinatorial charge-reversal mutagenesis\",\n      \"pmids\": [\"22532668\", \"20592019\", \"16407172\", \"18606678\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full conformational switching mechanism in MD-2 not directly observed\", \"Generalization to other partial lipid A structures incomplete\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Established that the MD-2 pocket can be engaged by non-LPS chemotypes to drive canonical TLR4 signaling, validating it as a versatile and druggable ligand-binding module.\",\n      \"evidence\": \"Crystal structure of Neoseptin-3 bound to mouse MD-2 with MyD88/TRIF-KO and CD14-independence validation; pocket binding of paclitaxel, curcumin, opioids, sulfatides and inhibitors\",\n      \"pmids\": [\"26831104\", \"18650420\", \"17609337\", \"19679181\", \"34290146\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endogenous physiological ligands beyond LPS incompletely catalogued\", \"In vivo relevance of some pocket ligands uncertain\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Extended MD-2 ligand repertoire to endogenous danger and acute-phase molecules (heme, SAA3, sCD83, Gb4), positioning MD-2 as a hub for sterile and endogenous TLR4 activation.\",\n      \"evidence\": \"Direct binding/pull-down, SPR, co-IP and mutagenesis with NF-κB readouts and KO mouse models\",\n      \"pmids\": [\"32695117\", \"23858030\", \"28193829\", \"23471986\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab binding evidence for several ligands\", \"Physiological concentrations and competition with LPS not resolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstrated therapeutic targeting of MD-2, with covalent Cys133 modification blocking TLR4 dimerization and reducing inflammation in disease models.\",\n      \"evidence\": \"Disulfiram covalent modification of Cys133, dimerization/reporter assays, macrophage cytokine assays and an MPTP Parkinson's mouse model\",\n      \"pmids\": [\"37487070\", \"26076332\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Selectivity of covalent inhibitors for MD-2 in vivo not fully established\", \"Translation to human disease unproven\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How MD-2 conformational switching couples ligand binding within the pocket to productive TLR4 dimerization and adaptor recruitment, and how the diverse endogenous ligands are physiologically prioritized, remain incompletely defined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No time-resolved structural view of pocket-to-dimerization signal transmission\", \"Competition hierarchy among endogenous MD-2 ligands unresolved\", \"Mechanism by which secreted MD-2 chaperones TLR4 export not molecularly defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [2, 4, 5]},\n      {\"term_id\": \"GO:0001618\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"GO:0038024\", \"supporting_discovery_ids\": [38, 39]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1, 16]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [1, 8, 16]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [38, 39]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 1, 5]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 5, 20]}\n    ],\n    \"complexes\": [\n      \"TLR4-MD-2 LPS receptor complex\",\n      \"TLR4-MD-2-LPS 2:2:2 signaling complex\",\n      \"LBP-CD14-MD-2 endotoxin transfer system\"\n    ],\n    \"partners\": [\n      \"TLR4\",\n      \"CD14\",\n      \"LBP\",\n      \"TLR2\",\n      \"SAA3\",\n      \"CD83\",\n      \"PTX3\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}