{"gene":"HLA-B","run_date":"2026-06-10T01:55:22","timeline":{"discoveries":[{"year":1976,"finding":"HLA-B specificities and the public antigens Bw4/Bw6 are distinct antigenic determinants located on the same polypeptide chain. Sequential immunoprecipitation experiments demonstrated that HLA-B7 and Bw6, which are genetically associated, are different epitopes on the same molecule, as are HLA-B12 and Bw4.","method":"Sequential immunoprecipitation with alloantisera on 125I-labeled, papain-solubilized lymphoblastoid cell membrane preparations","journal":"European journal of immunology","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct biochemical reconstitution via sequential immunoprecipitation establishing co-localization of specificities on single polypeptide; foundational result replicated conceptually by later sequence studies","pmids":["63373"],"is_preprint":false},{"year":1978,"finding":"Purified HLA-A and HLA-B molecules can be reconstituted into phospholipid vesicles with asymmetric orientation (COOH-terminus anchored in membrane, extracellular domain facing outward), and remain antigenically active in this state. Protease cleavage confirmed the membrane topology consistent with a type I transmembrane protein.","method":"Detergent solubilization, lipid vesicle reconstitution, protease cleavage, anti-β2-microglobulin binding, and complement-mediated cytotoxicity inhibition assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with multiple orthogonal functional and structural readouts in a single rigorous study","pmids":["356051"],"is_preprint":false},{"year":1979,"finding":"HLA-A and HLA-B heavy chains are synthesized with high-mannose oligosaccharides, associate with β2-microglobulin within the first 10–15 min after synthesis in the ER, undergo oligosaccharide processing to complex form ~30 min post-synthesis, and appear at the cell surface 60–80 min post-synthesis. β2-microglobulin association precedes and is required for conformational maturation.","method":"Pulse-chase metabolic labeling, immunoprecipitation with conformation-sensitive antisera, oligosaccharide processing analysis in human B-lymphoblastoid cells","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — pulse-chase kinetics with multiple antisera establishing precursor-product pathway; independently supported by PMID 7000762","pmids":["93026"],"is_preprint":false},{"year":1980,"finding":"HLA-A and HLA-B heavy chains are inserted asymmetrically into the rough ER as transmembrane polypeptides; β2-microglobulin association is necessary for subsequent oligosaccharide processing and intracellular transport to the cell surface, whereas glycosylation itself is not required for asymmetric insertion, transport, or surface expression.","method":"Pulse-chase biosynthetic labeling, subcellular fractionation, glycosylation inhibition (tunicamycin), and Daudi (β2m-deficient) cell line analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal approaches including loss-of-function (Daudi cells lacking β2m) and glycosylation inhibition, replicating and extending PMID 93026","pmids":["7000762"],"is_preprint":false},{"year":1989,"finding":"The Bw4 and Bw6 supertypic specificities of HLA-B are encoded by residues 74–83 in the α-helical region of the α1 domain. Bw6 is distinguished by Ser at position 77 and Asn at position 80; Bw4 is characterized by at least seven different amino acid exchange patterns at positions 77 and 80–83.","method":"Gene cloning, nucleotide sequencing of HLA-B38 and B39 alleles, sequence comparison, and monoclonal antibody reactivity mapping","journal":"Immunogenetics","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct sequencing combined with functional mAb epitope mapping; residue assignments independently confirmed by subsequent structural studies","pmids":["2777338"],"is_preprint":false},{"year":1994,"finding":"NKB1 (KIR3DL1), a 70-kD glycoprotein expressed on a subset of NK cells, is a receptor that specifically recognizes certain HLA-B alleles (e.g., HLA-B*5101, HLA-B*5801) but not HLA-A or HLA-C alleles. Anti-NKB1 mAb DX9 inhibits NK-cell lysis of target cells transfected with those specific HLA-B alleles.","method":"NK cell clonal assays, HLA-class-I-deficient cell transfection, mAb blocking experiments with DX9, flow cytometry","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — functional blocking by specific mAb with transfection controls; foundational identification of HLA-B as ligand for KIR3DL1, replicated broadly in later literature","pmids":["8046332"],"is_preprint":false},{"year":1997,"finding":"HLA-B*4801 binds nonamer peptides with Gln or Lys at position 2 and Leu at the C-terminus (peptide-binding motif). The allotype binds CD8α homodimers weakly due to Thr245 in the α3 domain; mutating Thr245→Ala restores CD8 binding to levels comparable to other HLA-I allotypes. Despite low CD8 affinity, alloreactive T cells recognizing B*4801 are still inhibited by anti-CD8 mAbs.","method":"Transfection into HLA-class-I-deficient 221 cells, pool sequence analysis of endogenous peptides, in vitro cell-cell CD8 binding assay, site-directed mutagenesis (T245A), flow cytometry","journal":"Tissue antigens","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis combined with in vitro binding assay and peptide motif analysis in a single study","pmids":["9331948"],"is_preprint":false},{"year":2002,"finding":"The activating NK receptor KIR3DS1, in epistatic combination with HLA-B alleles encoding Bw4-80Ile, delays progression to AIDS after HIV-1 infection. Neither locus alone conferred the protective effect; the strongest synergistic effect was on CD4+ T-cell depletion, consistent with KIR3DS1-mediated NK-cell activity triggered by HLA-B Bw4-80Ile ligands.","method":"Genetic epistasis analysis in >1,000 HIV-infected individuals; population-based association study with KIR and HLA typing","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — large-cohort epistasis study with consistent directional effects across multiple AIDS endpoints; replicated by PMID 17496894","pmids":["12134147"],"is_preprint":false},{"year":2007,"finding":"KIR3DL1 allotypes differing in NK cell expression levels and inhibitory capacity combine with HLA-B Bw4 allotypes to produce a hierarchy of effects on AIDS progression and HIV RNA levels. Higher-expression KIR3DL1 allotypes combined with HLA-B Bw4-80Ile provide the greatest protection, correlating with previously defined functional differences between KIR3DL1 allotypes.","method":"Large-cohort genetic association study (>1,500 HIV+ individuals) with KIR3DL1/HLA-B subtype genotyping; functional correlation with published NK cell assay data","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — large replicated cohort with allotype-specific functional correlation; extends PMID 12134147 with allelic resolution","pmids":["17496894"],"is_preprint":false},{"year":2009,"finding":"HLA-B*3503 (Phe116) shows reduced intracellular maturation rate and enhanced binding to TAP compared with HLA-B*3501 (Ser116), which differ only at position 116. Both allotypes are relatively tapasin-independent. The reduced peptide loading efficiency of HLA-B*3503 is proposed to account for its slower ER-Golgi trafficking and association with rapid AIDS progression.","method":"Pulse-chase labeling, TAP co-immunoprecipitation, in vitro peptide binding assay with peptide libraries, thermostability assay, intracellular trafficking analysis in HIV-infected and uninfected cells","journal":"Immunogenetics","confidence":"High","confidence_rationale":"Tier 1 / Moderate — multiple orthogonal in vitro and cellular assays in a single study with mutagenesis-like allelic comparison; single lab","pmids":["19838694"],"is_preprint":false},{"year":2012,"finding":"HLA-B*1502, loaded with endogenous peptide, directly binds carbamazepine (CBZ) without intracellular drug metabolism or antigen processing, and this trimolecular HLA-B*1502/peptide/β2m complex activates CBZ-specific cytotoxic T lymphocytes. Three residues (Asn63, Ile95, Leu156) in the peptide-binding groove are critical for CBZ presentation; Asn63 (shared by the B75 family) is the key residue. Structural modifications of the CBZ ring that abolish HLA-B*1502 binding also abolish CTL activation.","method":"Surface plasmon resonance, peptide-binding assay, site-directed mutagenesis of HLA-B*1502, CTL activation assays, computer modeling","journal":"The Journal of allergy and clinical immunology","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted direct drug-HLA binding by SPR combined with mutagenesis and functional CTL readout in a single rigorous study","pmids":["22322005"],"is_preprint":false},{"year":2014,"finding":"HLA-B polymorphisms profoundly influence tapasin dependence of assembly and the stability of peptide-deficient HLA-B forms. Certain HLA-B residues near the C-terminal end of the peptide-binding groove are key determinants of tapasin-independent assembly. Tapasin-independent allotypes assemble more readily with peptides in vitro and show reduced aggregation during refolding compared with tapasin-dependent allotypes of the same supertype.","method":"In vitro refolding assays, tapasin-deficient cell line expression, aggregation measurements, cell surface expression and stability assays across 27 HLA-B alleles","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 1 / Strong — systematic in vitro reconstitution across 27 alleles combined with cellular loss-of-function data, identifying structural determinants; single lab but multiple orthogonal methods","pmids":["24790147"],"is_preprint":false},{"year":2015,"finding":"KIR3DS1 recognizes HLA-B*57:01 in a peptide-dependent manner. Specific HIV-derived peptides presented by HLA-B*57:01 facilitate productive interactions with KIR3DS1, demonstrating that the peptide repertoire shapes KIR3DS1 engagement and thereby NK cell activation.","method":"Structure-driven peptide screening, KIR-HLA binding assays with defined peptide epitopes, functional NK cell assays","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding assays and functional NK readout with defined peptides; single lab, no crystal structure reported in abstract","pmids":["25740999"],"is_preprint":false},{"year":2016,"finding":"KIR3DL1 and HLA-B Bw4 subtypes calibrate NK cell education and effector capacity in a combinatorial, density-dependent manner. High-density KIR3DL1 paired with Bw4-80I HLA-B confers greatest NK reactivity against HLA-negative targets and HIV-infected CD4+ T cells. Binding strength between KIR3DL1 and HLA-B subtypes, receptor density, and ligand density are each functionally important determinants.","method":"Primary NK cell assays with defined KIR3DL1/HLA-B subtype donor combinations, cytotoxicity assays against HIV-infected autologous CD4+ T cells, flow cytometry for receptor/ligand density","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional primary cell assays with defined genetic combinations; single lab, multiple readouts","pmids":["26962229"],"is_preprint":false},{"year":2016,"finding":"HIV-1 Nef downregulates HLA-B less efficiently than HLA-A across 46 patient-derived Nef clones. Nef position 202 and the C-terminal CKV motif of HLA-A (absent in HLA-B) contribute to this differential downregulation. A Nef double mutation at positions 202 and the HLA cytoplasmic tail interaction site impairs HLA-A but not HLA-B downregulation, thereby increasing infected cell recognition by HIV-specific T cells.","method":"Flow cytometry of HLA surface expression on virus-infected cells, 46 primary Nef clones, site-directed mutagenesis of Nef (N202 variants), co-culture T cell recognition assays, in silico analysis","journal":"mBio","confidence":"High","confidence_rationale":"Tier 1 / Strong — site-directed mutagenesis combined with functional T cell recognition assay and natural sequence diversity analysis; single lab, multiple orthogonal methods","pmids":["26787826"],"is_preprint":false},{"year":2016,"finding":"HLA-B*27 subtypes associated with ankylosing spondylitis (B*27:04 and B*27:05) exhibit increased conformational flexibility (molecular dynamics) compared with non-associated subtypes (B*27:06 and B*27:09), as revealed by isotope-edited infrared spectroscopy. Crystal structures show that peptide presentation mode (dual vs. single conformation) does not strictly distinguish disease-associated from non-associated subtypes, whereas elevated molecular dynamics does.","method":"X-ray crystallography of pVIPR-HLA-B*27:04 and pVIPR-HLA-B*27:06 complexes, isotope-edited infrared (IR) spectroscopy to probe molecular dynamics","journal":"Arthritis & rheumatology","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures combined with spectroscopic dynamics measurement across four subtypes in a single study","pmids":["26748477"],"is_preprint":false},{"year":2017,"finding":"HLA-B*46:01, formed by intergenic mini-conversion incorporating a segment of HLA-C*01:02, carries the C1 epitope in its α1 domain and is consequently recognized by the C1-specific NK cell receptor KIR2DL3. High-resolution mass spectrometry showed that only the ~21% of HLA-B*46:01 peptides with specific C-terminal characteristics form KIR2DL3 ligands, demonstrating peptide-dependent KIR recognition.","method":"High-resolution mass spectrometry immunopeptidomics, KIR2DL3 binding assays with defined peptide subsets, sequence/structure analysis of the mini-conversion","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 / Strong — mass spectrometry peptidome combined with functional KIR binding assays establishing peptide-dependent NK recognition; single lab, multiple orthogonal methods","pmids":["28514659"],"is_preprint":false},{"year":2017,"finding":"KIR3DL1 and HLA-B subtype combinations predictive of weak NK inhibition are associated with significantly lower AML relapse and overall mortality after HCT. NK cells expressing strong-inhibitory KIR3DL1 subtypes are reproducibly inhibited by target cells with corresponding HLA-B subtypes in cytotoxic assays, whereas weak/non-inhibitory combinations allow greater cytotoxicity against AML.","method":"In vitro NK cytotoxicity assays with segregated KIR3DL1 subtypes and defined HLA-B subtype targets; clinical outcome analysis in 1,328 AML patients post-HCT","journal":"Journal of clinical oncology","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vitro functional hierarchy confirmed in large independent clinical cohort; replicated functional relationships from PMID 26962229","pmids":["28520526"],"is_preprint":false},{"year":2018,"finding":"HLA-B allotypes show highly variable cell surface expression levels and half-lives on primary lymphocytes, dependent on both allele and cell type. Low expression on lymphocytes for allotypes that bind peptides with Pro at position 2 is linked to TAP disfavoring such peptides; this low-expression phenotype is reversed in monocytes with larger intracellular HLA pools. These allele- and cell-dependent antigen acquisition pathway differences influence surface expression, stability, and receptivity to exogenous antigens.","method":"Multicolor flow cytometry, half-life measurements, endogenous peptide binding assays, cell fractionation in primary lymphocytes and monocytes from human donors","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal measurements in primary human cells across multiple alleles and cell types; single lab","pmids":["29989547"],"is_preprint":false},{"year":2018,"finding":"Approximately 15% of tested HLA-B allotypes (particularly HLA-B*35, HLA-B*57, and HLA-B*15 alleles) are expressed at relatively high levels on the surface of TAP1- or TAP2-deficient cells, indicating TAP-independent assembly. High peptide-loading efficiency, broad specificity for peptides from unconventional sources, and high intrinsic stability of the empty form combinatorially enable TAP-independent assembly. TAP-resistant allotypes are more resistant to viral TAP-inhibitor-induced HLA-I downmodulation and consequent NK activation.","method":"Expression of 27 HLA-B alleles in TAP1/TAP2-deficient cell lines, surface expression assays, endoglycosidase H sensitivity, in vitro peptide binding, viral TAP inhibitor challenge, NK activation assays","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 1 / Strong — systematic in vitro and cellular loss-of-function approach across 27 alleles with multiple mechanistic readouts; single lab but comprehensive","pmids":["29995954"],"is_preprint":false},{"year":2018,"finding":"Peptide-deficient (empty) HLA-B*35:01 heterodimers are thermostable, detectable on the cell surface, and preferentially bind CD8 via a CD8-dependent mode distinct from peptide-loaded HLA-I/TCR interactions. Empty HLA-B*35:01 tetramers bind a majority of blood-derived CD8+ T cells. These empty conformers do not directly activate CD8+ T cells but accumulate at the immunological synapse, enhance cell adhesion, and amplify cognate peptide-induced CD8+ T cell activation.","method":"Tetramer staining of primary CD8+ T cells, immunological synapse imaging, CD8 co-receptor blocking, adhesion and activation assays with peptide-deficient vs. peptide-loaded HLA-B*35:01","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal cellular assays establishing a new functional role for empty HLA-B conformers; single lab","pmids":["29741477"],"is_preprint":false},{"year":2018,"finding":"CD4+ T cell depletion prior to abacavir (ABC) administration in HLA-B*57:01 transgenic mice converts ABC tolerance into a reactive phenotype: DC maturation is enhanced, systemic ABC-reactive CD8+ T cells with effector/skin-homing phenotype are generated, and CD8+ infiltration occurs in drug-sensitized skin. B7 costimulatory molecule blockade prevents CD8+ T cell activation, placing costimulation as a requirement for the HLA-B*57:01-restricted ABC response.","method":"HLA-B*57:01 transgenic mouse model, CD4+ T cell depletion in vivo, DC maturation assays, flow cytometry, skin histology, B7 blockade experiments","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo transgenic model with genetic depletion and pharmacological blockade establishing mechanistic requirements; multiple orthogonal endpoints","pmids":["29782330"],"is_preprint":false},{"year":2019,"finding":"HCMV immunoevasin US11 degrades HLA-A molecules via ERAD but HLA-B locus products generally resist US11-mediated degradation, assemble with β2m, and exit the ER in the presence of US11. A low-complexity region of US11 (between signal peptide and Ig-like domain) is necessary for stable interaction with assembled MHC-I and also responsible for altering the HLA-B ligandome, suggesting a two-pronged viral immune evasion strategy.","method":"MHC-I peptide ligand mass spectrometry in HCMV-infected cells, US11 domain mutagenesis, co-immunoprecipitation, intracellular maturation assays","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 1 / Strong — domain mutagenesis of viral protein combined with peptidomics and co-IP establishing locus-specific mechanism; single lab, multiple orthogonal methods","pmids":["31527904"],"is_preprint":false},{"year":2019,"finding":"HLA-B and HLA-C organize differently at the cell surface nanoscale: HLA-C forms larger and more numerous clusters than HLA-B, with a greater proportion of HLA-C contributing to clusters, when expression level is controlled. Both HLA-B and HLA-C form more clusters at lower expression levels. HLA class I organization also varies with cell type (T cells more clustered than B cells).","method":"Super-resolution microscopy of three HLA-B allotypes and two HLA-C allotypes transfected into HLA-B/C-negative 721.221 cells, with expression-level controls","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct super-resolution imaging with controlled expression levels; single lab, single method","pmids":["30761133"],"is_preprint":false},{"year":2019,"finding":"Increased pro-inflammatory cytokine (TNFα/IFNγ) signaling upregulates HLA-B allomorph expression in lung cancer cells, independently driving significant changes in the HLA-bound immunopeptidome beyond those attributable to proteome changes.","method":"Quantitative proteomics, immunopeptidomics (LC-MS/MS), cytokine stimulation of lung cancer cells","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mass-spectrometry-based immunopeptidomics combined with proteomics in the same cells showing HLA-B-specific peptidome changes; single lab","pmids":["30833945"],"is_preprint":false},{"year":2020,"finding":"HLA-B knockdown in pancreatic cancer cells alters integrin beta-1 (ITGB1) expression and cell migration in a cell-line-dependent manner: HLA-B siRNA increases ITGB1 and migration in S2-013 cells but decreases both in PANC-1 and MIA PaCa-2 cells. A specific transmembrane sequence in the HLA-B heavy chain correlates with the direction of the migration effect.","method":"siRNA knockdown of HLA-B in three pancreatic cancer cell lines, transwell migration assays, Western blot for ITGB1","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with defined molecular readout (ITGB1) and functional phenotype (migration); single lab, single knockdown method, cell-line-dependent results reduce confidence","pmids":["32194036"],"is_preprint":false},{"year":2021,"finding":"Flucloxacillin (FLX) haptenates lysine residues on HLA-B*57:01-bound peptides, generating drug-modified neoantigens that drive CD8+ T cell responses. FLX-haptenated peptides at P4 and P6 positions are immunogenic in HLA-B*57:01 transgenic mice. FLX also covalently modifies K146 on the HLA-B*57:01 heavy chain itself, potentially interfering with KIR-3DL or peptide interactions.","method":"Mass spectrometry immunopeptidomics of FLX-treated B-LCL cells expressing HLA-B*57:01, synthesis and in vivo immunization of drug-conjugated peptides in transgenic mice, CD8+ T cell activation assays","journal":"Frontiers in immunology","confidence":"High","confidence_rationale":"Tier 1 / Strong — mass spectrometry identification combined with in vivo immunization and functional T cell assays establishing causal drug-peptide-HLA mechanism","pmids":["33633747"],"is_preprint":false},{"year":2021,"finding":"Extracellular vesicles over-represent HLA-B complexes and peptide ligands, including cysteinylated peptides, compared with whole cells of the same line. This differential antigen presentation landscape is driven in part by preferential HLA-B sorting into vesicles.","method":"HLA-I immunopeptidomics (LC-MS/MS) comparing extracellular vesicles versus whole-cell lysates from the same cell line","journal":"Communications biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mass spectrometry-based comparative immunopeptidomics; single lab, single cell line","pmids":["34211107"],"is_preprint":false},{"year":2022,"finding":"Autoimmunity-associated public TCRs using BV9-CDR3β motifs, expanded in AS joints and AAU eyes, recognize self-peptides and microbial peptides presented by HLA-B*27:05 in a shared binding motif. Structural analysis revealed the molecular basis of TCR cross-reactivity between self-antigens and microbial antigens at the HLA-B*27:05 peptide-binding groove.","method":"TCR isolation from blood/synovial/ocular T cells, HLA-B*27:05 yeast display peptide libraries, TCR activation assays, structural analysis of peptide-MHC-TCR complexes","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — structural determination combined with yeast display library screening and functional T cell activation assays identifying shared antigen binding motif","pmids":["36477533"],"is_preprint":false},{"year":2010,"finding":"Large-scale immunopeptidomics of HLA-B*2705 identified 1,268 B27-presented peptides, refining the binding motif and revealing both short canonical peptides and long peptides with bulging middle residues. Human cartilage-derived B27 peptides sharing sequence similarity with common bacterial sequences were identified as molecular mimicry candidates.","method":"Recombinant soluble HLA-B27 expression, capillary chromatography/tandem MS, SILAC and iTRAQ quantification from chondrocytic and HeLa cells","journal":"Arthritis and rheumatism","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — comprehensive mass spectrometry-based peptidome with stable isotope quantification; single lab, no functional T cell validation in this study","pmids":["20112406"],"is_preprint":false}],"current_model":"HLA-B encodes a highly polymorphic MHC class I heavy chain that assembles with β2-microglobulin and a peptide cargo in the ER (requiring β2m association for glycan processing and ER-Golgi transport), traffics to the cell surface as a type I transmembrane glycoprotein, and presents peptide antigens to CD8+ T cells and NK cells via KIR3DL1/KIR3DS1 receptors; polymorphisms at specific residues determine tapasin dependence, TAP dependence, peptide-binding motif, peptidome diversity, KIR binding specificity (Bw4/Bw6 epitopes at positions 77–83), resistance to viral immune evasion (relative resistance to HIV-1 Nef downregulation and HCMV US11-mediated ERAD), and susceptibility to drug-hypersensitivity reactions through direct drug binding within the peptide-binding groove."},"narrative":{"mechanistic_narrative":"HLA-B encodes a highly polymorphic MHC class I heavy chain that assembles with β2-microglobulin and a peptide cargo and traffics to the cell surface to present antigens to CD8+ T cells and NK cells [PMID:63373, PMID:93026]. The heavy chain is inserted asymmetrically into the rough ER as a type I transmembrane glycoprotein with its extracellular domain facing the lumen, and β2-microglobulin association — not glycosylation — is the prerequisite for conformational maturation, oligosaccharide processing, and ER-to-surface transport [PMID:356051, PMID:93026, PMID:7000762]. Allelic polymorphism governs nearly every functional property of the molecule: residues near the C-terminal end of the peptide-binding groove set tapasin dependence and the stability of peptide-deficient forms [PMID:24790147], while a subset of allotypes achieve TAP-independent assembly through high peptide-loading efficiency and high intrinsic stability of the empty heterodimer [PMID:29995954]. Polymorphisms also dictate the peptide-binding motif and peptidome breadth, intracellular maturation rate, and surface expression in an allele- and cell-type-dependent manner [PMID:9331948, PMID:19838694, PMID:29989547]. The Bw4/Bw6 supertypic epitopes encoded by residues 74–83 of the α1 domain [PMID:2777338] determine recognition by the NK-cell receptors KIR3DL1 and KIR3DS1, where the combination of receptor allotype/density and HLA-B Bw4 subtype calibrates NK education and effector function — a combinatorial logic with consequences for HIV/AIDS progression and post-transplant AML outcomes [PMID:8046332, PMID:12134147, PMID:17496894, PMID:26962229, PMID:28520526]. Such NK recognition is peptide-dependent, as shown for KIR3DS1 engagement of HLA-B*57:01 and KIR2DL3 recognition of the C1-bearing HLA-B*46:01 [PMID:25740999, PMID:28514659]. HLA-B is also a determinant of viral immune evasion, resisting HIV-1 Nef downregulation and HCMV US11-mediated ERAD relative to HLA-A [PMID:26787826, PMID:31527904]. Finally, specific allotypes mediate drug-hypersensitivity reactions through direct, processing-independent drug binding within the peptide-binding groove or covalent haptenation of bound peptides, as established for carbamazepine on HLA-B*1502 and abacavir/flucloxacillin on HLA-B*57:01 [PMID:22322005, PMID:29782330, PMID:33633747], and HLA-B*27 subtypes present self and microbial peptides to autoreactive public TCRs in spondyloarthritis [PMID:36477533].","teleology":[{"year":1976,"claim":"Established that HLA-B private specificities and the public Bw4/Bw6 antigens are distinct epitopes carried on a single polypeptide, defining the molecular target as one heavy chain rather than separate molecules.","evidence":"Sequential immunoprecipitation with alloantisera on radiolabeled, papain-solubilized lymphoblastoid membranes","pmids":["63373"],"confidence":"High","gaps":["Did not define the amino acid residues encoding the epitopes","No structural model of the heavy chain"]},{"year":1980,"claim":"Defined the biosynthetic and topological logic of the molecule — type I transmembrane insertion into the ER with β2m association as the obligatory step for maturation and surface transport — answering how the heavy chain becomes a functional surface glycoprotein.","evidence":"Lipid vesicle reconstitution with protease topology mapping; pulse-chase labeling with glycosylation inhibition and β2m-deficient Daudi cells","pmids":["356051","93026","7000762"],"confidence":"High","gaps":["Did not identify the chaperone machinery (tapasin/TAP) controlling peptide loading","Allele-specific differences in maturation not addressed"]},{"year":1989,"claim":"Mapped the Bw4/Bw6 supertypic specificities to residues 74–83 of the α1 helix, providing the structural basis later linking HLA-B polymorphism to NK receptor recognition.","evidence":"Allele cloning, nucleotide sequencing, and monoclonal antibody epitope mapping","pmids":["2777338"],"confidence":"High","gaps":["No receptor for these epitopes yet identified","Functional consequence of the epitope not established"]},{"year":1997,"claim":"Showed that HLA-B allotypes carry defined peptide-binding motifs and that an α3-domain residue (Thr245) tunes CD8 co-receptor binding, linking polymorphism to both peptide selection and CD8 engagement.","evidence":"Transfection, pool peptide sequencing, in vitro CD8 binding, and T245A site-directed mutagenesis","pmids":["9331948"],"confidence":"High","gaps":["CD8-binding effect characterized for a single allotype","Physiological consequence of weak CD8 binding incompletely resolved"]},{"year":1994,"claim":"Identified HLA-B as the specific ligand for the NK receptor KIR3DL1, establishing HLA-B's role in NK cell recognition beyond T cell antigen presentation.","evidence":"NK clonal cytotoxicity, HLA-allele transfection, and DX9 mAb blocking","pmids":["8046332"],"confidence":"High","gaps":["Did not define which residues confer KIR3DL1 specificity","Peptide-dependence of recognition not addressed"]},{"year":2008,"claim":"Demonstrated that KIR3DL1/KIR3DS1 allotypes act epistatically with HLA-B Bw4 subtypes to modulate HIV/AIDS progression in a density- and binding-strength-dependent hierarchy, translating the molecular ligand relationship into in vivo immune control.","evidence":"Large-cohort genetic epistasis association studies of KIR and HLA-B subtypes in HIV-infected individuals","pmids":["12134147","17496894"],"confidence":"High","gaps":["Genetic association does not establish the molecular mechanism of NK activation at the cellular level","Causal peptide contribution not yet tested"]},{"year":2009,"claim":"Showed that a single residue (position 116) controls peptide-loading efficiency, TAP binding, and maturation rate, linking fine allelic variation to trafficking kinetics and AIDS progression rate.","evidence":"Pulse-chase, TAP co-IP, peptide-binding and thermostability assays comparing HLA-B*3501 vs *3503","pmids":["19838694"],"confidence":"High","gaps":["Single allele pair from a single lab","Direct in vivo link between trafficking kinetics and clinical outcome not proven"]},{"year":2014,"claim":"Systematically defined polymorphic determinants of tapasin dependence and empty-form stability across 27 alleles, explaining why HLA-B allotypes differ in their assembly requirements.","evidence":"In vitro refolding, aggregation, and tapasin-deficient cell expression across 27 HLA-B alleles","pmids":["24790147"],"confidence":"High","gaps":["Single lab","Precise structural mechanism of residue effects on tapasin engagement not crystallographically defined"]},{"year":2018,"claim":"Established TAP-independent assembly as a property of a subset of allotypes and connected it to resistance to viral TAP inhibitors, and revealed allele/cell-type-dependent surface expression and a non-canonical adhesion-amplifying role for empty HLA-B conformers.","evidence":"Expression of 27 alleles in TAP-deficient cells, peptide-binding and NK assays; primary-cell flow cytometry; tetramer/synapse imaging of empty HLA-B*35:01","pmids":["29995954","29989547","29741477"],"confidence":"High","gaps":["Generality of empty-conformer adhesion role across allotypes unknown","In vivo relevance of TAP-independence to infection control not directly demonstrated"]},{"year":2017,"claim":"Demonstrated peptide-dependence of NK recognition for HLA-B, including KIR3DS1 engagement of HLA-B*57:01 and KIR2DL3 recognition of a C1-epitope HLA-B*46:01 generated by intergenic mini-conversion, refining the rules of NK ligand formation.","evidence":"Defined-peptide KIR binding/NK functional assays; high-resolution immunopeptidomics with KIR2DL3 binding of peptide subsets","pmids":["25740999","28514659"],"confidence":"Medium","gaps":["No crystal structures of these peptide-KIR complexes reported","Quantitative contribution of peptide identity to NK activation in vivo unresolved"]},{"year":2016,"claim":"Defined HLA-B as a relatively resistant target of viral immune evasion, with locus-specific resistance to HIV-1 Nef downregulation and HCMV US11-mediated ERAD, mapping the viral and host sequence determinants of differential targeting.","evidence":"Nef clone panel with site-directed mutagenesis and T cell recognition assays; US11 domain mutagenesis with peptidomics and co-IP","pmids":["26787826","31527904"],"confidence":"High","gaps":["Structural basis of HLA-B resistance to US11/Nef not fully resolved","Whether resistance generalizes across all HLA-B allotypes untested"]},{"year":2012,"claim":"Established that HLA-B mediates drug hypersensitivity through direct, metabolism-independent drug binding within the peptide-binding groove and through peptide haptenation, identifying causal residues and demonstrating CD8+ T cell activation.","evidence":"SPR drug-HLA binding, mutagenesis, and CTL assays (carbamazepine/HLA-B*1502); transgenic mouse and 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Sequential immunoprecipitation experiments demonstrated that HLA-B7 and Bw6, which are genetically associated, are different epitopes on the same molecule, as are HLA-B12 and Bw4.\",\n      \"method\": \"Sequential immunoprecipitation with alloantisera on 125I-labeled, papain-solubilized lymphoblastoid cell membrane preparations\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct biochemical reconstitution via sequential immunoprecipitation establishing co-localization of specificities on single polypeptide; foundational result replicated conceptually by later sequence studies\",\n      \"pmids\": [\"63373\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1978,\n      \"finding\": \"Purified HLA-A and HLA-B molecules can be reconstituted into phospholipid vesicles with asymmetric orientation (COOH-terminus anchored in membrane, extracellular domain facing outward), and remain antigenically active in this state. Protease cleavage confirmed the membrane topology consistent with a type I transmembrane protein.\",\n      \"method\": \"Detergent solubilization, lipid vesicle reconstitution, protease cleavage, anti-β2-microglobulin binding, and complement-mediated cytotoxicity inhibition assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with multiple orthogonal functional and structural readouts in a single rigorous study\",\n      \"pmids\": [\"356051\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1979,\n      \"finding\": \"HLA-A and HLA-B heavy chains are synthesized with high-mannose oligosaccharides, associate with β2-microglobulin within the first 10–15 min after synthesis in the ER, undergo oligosaccharide processing to complex form ~30 min post-synthesis, and appear at the cell surface 60–80 min post-synthesis. β2-microglobulin association precedes and is required for conformational maturation.\",\n      \"method\": \"Pulse-chase metabolic labeling, immunoprecipitation with conformation-sensitive antisera, oligosaccharide processing analysis in human B-lymphoblastoid cells\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — pulse-chase kinetics with multiple antisera establishing precursor-product pathway; independently supported by PMID 7000762\",\n      \"pmids\": [\"93026\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1980,\n      \"finding\": \"HLA-A and HLA-B heavy chains are inserted asymmetrically into the rough ER as transmembrane polypeptides; β2-microglobulin association is necessary for subsequent oligosaccharide processing and intracellular transport to the cell surface, whereas glycosylation itself is not required for asymmetric insertion, transport, or surface expression.\",\n      \"method\": \"Pulse-chase biosynthetic labeling, subcellular fractionation, glycosylation inhibition (tunicamycin), and Daudi (β2m-deficient) cell line analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal approaches including loss-of-function (Daudi cells lacking β2m) and glycosylation inhibition, replicating and extending PMID 93026\",\n      \"pmids\": [\"7000762\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1989,\n      \"finding\": \"The Bw4 and Bw6 supertypic specificities of HLA-B are encoded by residues 74–83 in the α-helical region of the α1 domain. Bw6 is distinguished by Ser at position 77 and Asn at position 80; Bw4 is characterized by at least seven different amino acid exchange patterns at positions 77 and 80–83.\",\n      \"method\": \"Gene cloning, nucleotide sequencing of HLA-B38 and B39 alleles, sequence comparison, and monoclonal antibody reactivity mapping\",\n      \"journal\": \"Immunogenetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct sequencing combined with functional mAb epitope mapping; residue assignments independently confirmed by subsequent structural studies\",\n      \"pmids\": [\"2777338\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"NKB1 (KIR3DL1), a 70-kD glycoprotein expressed on a subset of NK cells, is a receptor that specifically recognizes certain HLA-B alleles (e.g., HLA-B*5101, HLA-B*5801) but not HLA-A or HLA-C alleles. Anti-NKB1 mAb DX9 inhibits NK-cell lysis of target cells transfected with those specific HLA-B alleles.\",\n      \"method\": \"NK cell clonal assays, HLA-class-I-deficient cell transfection, mAb blocking experiments with DX9, flow cytometry\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — functional blocking by specific mAb with transfection controls; foundational identification of HLA-B as ligand for KIR3DL1, replicated broadly in later literature\",\n      \"pmids\": [\"8046332\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"HLA-B*4801 binds nonamer peptides with Gln or Lys at position 2 and Leu at the C-terminus (peptide-binding motif). The allotype binds CD8α homodimers weakly due to Thr245 in the α3 domain; mutating Thr245→Ala restores CD8 binding to levels comparable to other HLA-I allotypes. Despite low CD8 affinity, alloreactive T cells recognizing B*4801 are still inhibited by anti-CD8 mAbs.\",\n      \"method\": \"Transfection into HLA-class-I-deficient 221 cells, pool sequence analysis of endogenous peptides, in vitro cell-cell CD8 binding assay, site-directed mutagenesis (T245A), flow cytometry\",\n      \"journal\": \"Tissue antigens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis combined with in vitro binding assay and peptide motif analysis in a single study\",\n      \"pmids\": [\"9331948\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"The activating NK receptor KIR3DS1, in epistatic combination with HLA-B alleles encoding Bw4-80Ile, delays progression to AIDS after HIV-1 infection. Neither locus alone conferred the protective effect; the strongest synergistic effect was on CD4+ T-cell depletion, consistent with KIR3DS1-mediated NK-cell activity triggered by HLA-B Bw4-80Ile ligands.\",\n      \"method\": \"Genetic epistasis analysis in >1,000 HIV-infected individuals; population-based association study with KIR and HLA typing\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — large-cohort epistasis study with consistent directional effects across multiple AIDS endpoints; replicated by PMID 17496894\",\n      \"pmids\": [\"12134147\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"KIR3DL1 allotypes differing in NK cell expression levels and inhibitory capacity combine with HLA-B Bw4 allotypes to produce a hierarchy of effects on AIDS progression and HIV RNA levels. Higher-expression KIR3DL1 allotypes combined with HLA-B Bw4-80Ile provide the greatest protection, correlating with previously defined functional differences between KIR3DL1 allotypes.\",\n      \"method\": \"Large-cohort genetic association study (>1,500 HIV+ individuals) with KIR3DL1/HLA-B subtype genotyping; functional correlation with published NK cell assay data\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — large replicated cohort with allotype-specific functional correlation; extends PMID 12134147 with allelic resolution\",\n      \"pmids\": [\"17496894\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"HLA-B*3503 (Phe116) shows reduced intracellular maturation rate and enhanced binding to TAP compared with HLA-B*3501 (Ser116), which differ only at position 116. Both allotypes are relatively tapasin-independent. The reduced peptide loading efficiency of HLA-B*3503 is proposed to account for its slower ER-Golgi trafficking and association with rapid AIDS progression.\",\n      \"method\": \"Pulse-chase labeling, TAP co-immunoprecipitation, in vitro peptide binding assay with peptide libraries, thermostability assay, intracellular trafficking analysis in HIV-infected and uninfected cells\",\n      \"journal\": \"Immunogenetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — multiple orthogonal in vitro and cellular assays in a single study with mutagenesis-like allelic comparison; single lab\",\n      \"pmids\": [\"19838694\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"HLA-B*1502, loaded with endogenous peptide, directly binds carbamazepine (CBZ) without intracellular drug metabolism or antigen processing, and this trimolecular HLA-B*1502/peptide/β2m complex activates CBZ-specific cytotoxic T lymphocytes. Three residues (Asn63, Ile95, Leu156) in the peptide-binding groove are critical for CBZ presentation; Asn63 (shared by the B75 family) is the key residue. Structural modifications of the CBZ ring that abolish HLA-B*1502 binding also abolish CTL activation.\",\n      \"method\": \"Surface plasmon resonance, peptide-binding assay, site-directed mutagenesis of HLA-B*1502, CTL activation assays, computer modeling\",\n      \"journal\": \"The Journal of allergy and clinical immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted direct drug-HLA binding by SPR combined with mutagenesis and functional CTL readout in a single rigorous study\",\n      \"pmids\": [\"22322005\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"HLA-B polymorphisms profoundly influence tapasin dependence of assembly and the stability of peptide-deficient HLA-B forms. Certain HLA-B residues near the C-terminal end of the peptide-binding groove are key determinants of tapasin-independent assembly. Tapasin-independent allotypes assemble more readily with peptides in vitro and show reduced aggregation during refolding compared with tapasin-dependent allotypes of the same supertype.\",\n      \"method\": \"In vitro refolding assays, tapasin-deficient cell line expression, aggregation measurements, cell surface expression and stability assays across 27 HLA-B alleles\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — systematic in vitro reconstitution across 27 alleles combined with cellular loss-of-function data, identifying structural determinants; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"24790147\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"KIR3DS1 recognizes HLA-B*57:01 in a peptide-dependent manner. Specific HIV-derived peptides presented by HLA-B*57:01 facilitate productive interactions with KIR3DS1, demonstrating that the peptide repertoire shapes KIR3DS1 engagement and thereby NK cell activation.\",\n      \"method\": \"Structure-driven peptide screening, KIR-HLA binding assays with defined peptide epitopes, functional NK cell assays\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding assays and functional NK readout with defined peptides; single lab, no crystal structure reported in abstract\",\n      \"pmids\": [\"25740999\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"KIR3DL1 and HLA-B Bw4 subtypes calibrate NK cell education and effector capacity in a combinatorial, density-dependent manner. High-density KIR3DL1 paired with Bw4-80I HLA-B confers greatest NK reactivity against HLA-negative targets and HIV-infected CD4+ T cells. Binding strength between KIR3DL1 and HLA-B subtypes, receptor density, and ligand density are each functionally important determinants.\",\n      \"method\": \"Primary NK cell assays with defined KIR3DL1/HLA-B subtype donor combinations, cytotoxicity assays against HIV-infected autologous CD4+ T cells, flow cytometry for receptor/ligand density\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional primary cell assays with defined genetic combinations; single lab, multiple readouts\",\n      \"pmids\": [\"26962229\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"HIV-1 Nef downregulates HLA-B less efficiently than HLA-A across 46 patient-derived Nef clones. Nef position 202 and the C-terminal CKV motif of HLA-A (absent in HLA-B) contribute to this differential downregulation. A Nef double mutation at positions 202 and the HLA cytoplasmic tail interaction site impairs HLA-A but not HLA-B downregulation, thereby increasing infected cell recognition by HIV-specific T cells.\",\n      \"method\": \"Flow cytometry of HLA surface expression on virus-infected cells, 46 primary Nef clones, site-directed mutagenesis of Nef (N202 variants), co-culture T cell recognition assays, in silico analysis\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — site-directed mutagenesis combined with functional T cell recognition assay and natural sequence diversity analysis; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"26787826\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"HLA-B*27 subtypes associated with ankylosing spondylitis (B*27:04 and B*27:05) exhibit increased conformational flexibility (molecular dynamics) compared with non-associated subtypes (B*27:06 and B*27:09), as revealed by isotope-edited infrared spectroscopy. Crystal structures show that peptide presentation mode (dual vs. single conformation) does not strictly distinguish disease-associated from non-associated subtypes, whereas elevated molecular dynamics does.\",\n      \"method\": \"X-ray crystallography of pVIPR-HLA-B*27:04 and pVIPR-HLA-B*27:06 complexes, isotope-edited infrared (IR) spectroscopy to probe molecular dynamics\",\n      \"journal\": \"Arthritis & rheumatology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures combined with spectroscopic dynamics measurement across four subtypes in a single study\",\n      \"pmids\": [\"26748477\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"HLA-B*46:01, formed by intergenic mini-conversion incorporating a segment of HLA-C*01:02, carries the C1 epitope in its α1 domain and is consequently recognized by the C1-specific NK cell receptor KIR2DL3. High-resolution mass spectrometry showed that only the ~21% of HLA-B*46:01 peptides with specific C-terminal characteristics form KIR2DL3 ligands, demonstrating peptide-dependent KIR recognition.\",\n      \"method\": \"High-resolution mass spectrometry immunopeptidomics, KIR2DL3 binding assays with defined peptide subsets, sequence/structure analysis of the mini-conversion\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mass spectrometry peptidome combined with functional KIR binding assays establishing peptide-dependent NK recognition; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"28514659\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"KIR3DL1 and HLA-B subtype combinations predictive of weak NK inhibition are associated with significantly lower AML relapse and overall mortality after HCT. NK cells expressing strong-inhibitory KIR3DL1 subtypes are reproducibly inhibited by target cells with corresponding HLA-B subtypes in cytotoxic assays, whereas weak/non-inhibitory combinations allow greater cytotoxicity against AML.\",\n      \"method\": \"In vitro NK cytotoxicity assays with segregated KIR3DL1 subtypes and defined HLA-B subtype targets; clinical outcome analysis in 1,328 AML patients post-HCT\",\n      \"journal\": \"Journal of clinical oncology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vitro functional hierarchy confirmed in large independent clinical cohort; replicated functional relationships from PMID 26962229\",\n      \"pmids\": [\"28520526\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"HLA-B allotypes show highly variable cell surface expression levels and half-lives on primary lymphocytes, dependent on both allele and cell type. Low expression on lymphocytes for allotypes that bind peptides with Pro at position 2 is linked to TAP disfavoring such peptides; this low-expression phenotype is reversed in monocytes with larger intracellular HLA pools. These allele- and cell-dependent antigen acquisition pathway differences influence surface expression, stability, and receptivity to exogenous antigens.\",\n      \"method\": \"Multicolor flow cytometry, half-life measurements, endogenous peptide binding assays, cell fractionation in primary lymphocytes and monocytes from human donors\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal measurements in primary human cells across multiple alleles and cell types; single lab\",\n      \"pmids\": [\"29989547\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Approximately 15% of tested HLA-B allotypes (particularly HLA-B*35, HLA-B*57, and HLA-B*15 alleles) are expressed at relatively high levels on the surface of TAP1- or TAP2-deficient cells, indicating TAP-independent assembly. High peptide-loading efficiency, broad specificity for peptides from unconventional sources, and high intrinsic stability of the empty form combinatorially enable TAP-independent assembly. TAP-resistant allotypes are more resistant to viral TAP-inhibitor-induced HLA-I downmodulation and consequent NK activation.\",\n      \"method\": \"Expression of 27 HLA-B alleles in TAP1/TAP2-deficient cell lines, surface expression assays, endoglycosidase H sensitivity, in vitro peptide binding, viral TAP inhibitor challenge, NK activation assays\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — systematic in vitro and cellular loss-of-function approach across 27 alleles with multiple mechanistic readouts; single lab but comprehensive\",\n      \"pmids\": [\"29995954\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Peptide-deficient (empty) HLA-B*35:01 heterodimers are thermostable, detectable on the cell surface, and preferentially bind CD8 via a CD8-dependent mode distinct from peptide-loaded HLA-I/TCR interactions. Empty HLA-B*35:01 tetramers bind a majority of blood-derived CD8+ T cells. These empty conformers do not directly activate CD8+ T cells but accumulate at the immunological synapse, enhance cell adhesion, and amplify cognate peptide-induced CD8+ T cell activation.\",\n      \"method\": \"Tetramer staining of primary CD8+ T cells, immunological synapse imaging, CD8 co-receptor blocking, adhesion and activation assays with peptide-deficient vs. peptide-loaded HLA-B*35:01\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal cellular assays establishing a new functional role for empty HLA-B conformers; single lab\",\n      \"pmids\": [\"29741477\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CD4+ T cell depletion prior to abacavir (ABC) administration in HLA-B*57:01 transgenic mice converts ABC tolerance into a reactive phenotype: DC maturation is enhanced, systemic ABC-reactive CD8+ T cells with effector/skin-homing phenotype are generated, and CD8+ infiltration occurs in drug-sensitized skin. B7 costimulatory molecule blockade prevents CD8+ T cell activation, placing costimulation as a requirement for the HLA-B*57:01-restricted ABC response.\",\n      \"method\": \"HLA-B*57:01 transgenic mouse model, CD4+ T cell depletion in vivo, DC maturation assays, flow cytometry, skin histology, B7 blockade experiments\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo transgenic model with genetic depletion and pharmacological blockade establishing mechanistic requirements; multiple orthogonal endpoints\",\n      \"pmids\": [\"29782330\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"HCMV immunoevasin US11 degrades HLA-A molecules via ERAD but HLA-B locus products generally resist US11-mediated degradation, assemble with β2m, and exit the ER in the presence of US11. A low-complexity region of US11 (between signal peptide and Ig-like domain) is necessary for stable interaction with assembled MHC-I and also responsible for altering the HLA-B ligandome, suggesting a two-pronged viral immune evasion strategy.\",\n      \"method\": \"MHC-I peptide ligand mass spectrometry in HCMV-infected cells, US11 domain mutagenesis, co-immunoprecipitation, intracellular maturation assays\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — domain mutagenesis of viral protein combined with peptidomics and co-IP establishing locus-specific mechanism; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"31527904\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"HLA-B and HLA-C organize differently at the cell surface nanoscale: HLA-C forms larger and more numerous clusters than HLA-B, with a greater proportion of HLA-C contributing to clusters, when expression level is controlled. Both HLA-B and HLA-C form more clusters at lower expression levels. HLA class I organization also varies with cell type (T cells more clustered than B cells).\",\n      \"method\": \"Super-resolution microscopy of three HLA-B allotypes and two HLA-C allotypes transfected into HLA-B/C-negative 721.221 cells, with expression-level controls\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct super-resolution imaging with controlled expression levels; single lab, single method\",\n      \"pmids\": [\"30761133\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Increased pro-inflammatory cytokine (TNFα/IFNγ) signaling upregulates HLA-B allomorph expression in lung cancer cells, independently driving significant changes in the HLA-bound immunopeptidome beyond those attributable to proteome changes.\",\n      \"method\": \"Quantitative proteomics, immunopeptidomics (LC-MS/MS), cytokine stimulation of lung cancer cells\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mass-spectrometry-based immunopeptidomics combined with proteomics in the same cells showing HLA-B-specific peptidome changes; single lab\",\n      \"pmids\": [\"30833945\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"HLA-B knockdown in pancreatic cancer cells alters integrin beta-1 (ITGB1) expression and cell migration in a cell-line-dependent manner: HLA-B siRNA increases ITGB1 and migration in S2-013 cells but decreases both in PANC-1 and MIA PaCa-2 cells. A specific transmembrane sequence in the HLA-B heavy chain correlates with the direction of the migration effect.\",\n      \"method\": \"siRNA knockdown of HLA-B in three pancreatic cancer cell lines, transwell migration assays, Western blot for ITGB1\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with defined molecular readout (ITGB1) and functional phenotype (migration); single lab, single knockdown method, cell-line-dependent results reduce confidence\",\n      \"pmids\": [\"32194036\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Flucloxacillin (FLX) haptenates lysine residues on HLA-B*57:01-bound peptides, generating drug-modified neoantigens that drive CD8+ T cell responses. FLX-haptenated peptides at P4 and P6 positions are immunogenic in HLA-B*57:01 transgenic mice. FLX also covalently modifies K146 on the HLA-B*57:01 heavy chain itself, potentially interfering with KIR-3DL or peptide interactions.\",\n      \"method\": \"Mass spectrometry immunopeptidomics of FLX-treated B-LCL cells expressing HLA-B*57:01, synthesis and in vivo immunization of drug-conjugated peptides in transgenic mice, CD8+ T cell activation assays\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mass spectrometry identification combined with in vivo immunization and functional T cell assays establishing causal drug-peptide-HLA mechanism\",\n      \"pmids\": [\"33633747\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Extracellular vesicles over-represent HLA-B complexes and peptide ligands, including cysteinylated peptides, compared with whole cells of the same line. This differential antigen presentation landscape is driven in part by preferential HLA-B sorting into vesicles.\",\n      \"method\": \"HLA-I immunopeptidomics (LC-MS/MS) comparing extracellular vesicles versus whole-cell lysates from the same cell line\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mass spectrometry-based comparative immunopeptidomics; single lab, single cell line\",\n      \"pmids\": [\"34211107\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Autoimmunity-associated public TCRs using BV9-CDR3β motifs, expanded in AS joints and AAU eyes, recognize self-peptides and microbial peptides presented by HLA-B*27:05 in a shared binding motif. Structural analysis revealed the molecular basis of TCR cross-reactivity between self-antigens and microbial antigens at the HLA-B*27:05 peptide-binding groove.\",\n      \"method\": \"TCR isolation from blood/synovial/ocular T cells, HLA-B*27:05 yeast display peptide libraries, TCR activation assays, structural analysis of peptide-MHC-TCR complexes\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — structural determination combined with yeast display library screening and functional T cell activation assays identifying shared antigen binding motif\",\n      \"pmids\": [\"36477533\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Large-scale immunopeptidomics of HLA-B*2705 identified 1,268 B27-presented peptides, refining the binding motif and revealing both short canonical peptides and long peptides with bulging middle residues. Human cartilage-derived B27 peptides sharing sequence similarity with common bacterial sequences were identified as molecular mimicry candidates.\",\n      \"method\": \"Recombinant soluble HLA-B27 expression, capillary chromatography/tandem MS, SILAC and iTRAQ quantification from chondrocytic and HeLa cells\",\n      \"journal\": \"Arthritis and rheumatism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — comprehensive mass spectrometry-based peptidome with stable isotope quantification; single lab, no functional T cell validation in this study\",\n      \"pmids\": [\"20112406\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"HLA-B encodes a highly polymorphic MHC class I heavy chain that assembles with β2-microglobulin and a peptide cargo in the ER (requiring β2m association for glycan processing and ER-Golgi transport), traffics to the cell surface as a type I transmembrane glycoprotein, and presents peptide antigens to CD8+ T cells and NK cells via KIR3DL1/KIR3DS1 receptors; polymorphisms at specific residues determine tapasin dependence, TAP dependence, peptide-binding motif, peptidome diversity, KIR binding specificity (Bw4/Bw6 epitopes at positions 77–83), resistance to viral immune evasion (relative resistance to HIV-1 Nef downregulation and HCMV US11-mediated ERAD), and susceptibility to drug-hypersensitivity reactions through direct drug binding within the peptide-binding groove.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"HLA-B encodes a highly polymorphic MHC class I heavy chain that assembles with β2-microglobulin and a peptide cargo and traffics to the cell surface to present antigens to CD8+ T cells and NK cells [#0, #2]. The heavy chain is inserted asymmetrically into the rough ER as a type I transmembrane glycoprotein with its extracellular domain facing the lumen, and β2-microglobulin association — not glycosylation — is the prerequisite for conformational maturation, oligosaccharide processing, and ER-to-surface transport [#1, #2, #3]. Allelic polymorphism governs nearly every functional property of the molecule: residues near the C-terminal end of the peptide-binding groove set tapasin dependence and the stability of peptide-deficient forms [#11], while a subset of allotypes achieve TAP-independent assembly through high peptide-loading efficiency and high intrinsic stability of the empty heterodimer [#19]. Polymorphisms also dictate the peptide-binding motif and peptidome breadth, intracellular maturation rate, and surface expression in an allele- and cell-type-dependent manner [#6, #9, #18]. The Bw4/Bw6 supertypic epitopes encoded by residues 74–83 of the α1 domain [#4] determine recognition by the NK-cell receptors KIR3DL1 and KIR3DS1, where the combination of receptor allotype/density and HLA-B Bw4 subtype calibrates NK education and effector function — a combinatorial logic with consequences for HIV/AIDS progression and post-transplant AML outcomes [#5, #7, #8, #13, #17]. Such NK recognition is peptide-dependent, as shown for KIR3DS1 engagement of HLA-B*57:01 and KIR2DL3 recognition of the C1-bearing HLA-B*46:01 [#12, #16]. HLA-B is also a determinant of viral immune evasion, resisting HIV-1 Nef downregulation and HCMV US11-mediated ERAD relative to HLA-A [#14, #22]. Finally, specific allotypes mediate drug-hypersensitivity reactions through direct, processing-independent drug binding within the peptide-binding groove or covalent haptenation of bound peptides, as established for carbamazepine on HLA-B*1502 and abacavir/flucloxacillin on HLA-B*57:01 [#10, #21, #26], and HLA-B*27 subtypes present self and microbial peptides to autoreactive public TCRs in spondyloarthritis [#28].\",\n  \"teleology\": [\n    {\n      \"year\": 1976,\n      \"claim\": \"Established that HLA-B private specificities and the public Bw4/Bw6 antigens are distinct epitopes carried on a single polypeptide, defining the molecular target as one heavy chain rather than separate molecules.\",\n      \"evidence\": \"Sequential immunoprecipitation with alloantisera on radiolabeled, papain-solubilized lymphoblastoid membranes\",\n      \"pmids\": [\"63373\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the amino acid residues encoding the epitopes\", \"No structural model of the heavy chain\"]\n    },\n    {\n      \"year\": 1980,\n      \"claim\": \"Defined the biosynthetic and topological logic of the molecule — type I transmembrane insertion into the ER with β2m association as the obligatory step for maturation and surface transport — answering how the heavy chain becomes a functional surface glycoprotein.\",\n      \"evidence\": \"Lipid vesicle reconstitution with protease topology mapping; pulse-chase labeling with glycosylation inhibition and β2m-deficient Daudi cells\",\n      \"pmids\": [\"356051\", \"93026\", \"7000762\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the chaperone machinery (tapasin/TAP) controlling peptide loading\", \"Allele-specific differences in maturation not addressed\"]\n    },\n    {\n      \"year\": 1989,\n      \"claim\": \"Mapped the Bw4/Bw6 supertypic specificities to residues 74–83 of the α1 helix, providing the structural basis later linking HLA-B polymorphism to NK receptor recognition.\",\n      \"evidence\": \"Allele cloning, nucleotide sequencing, and monoclonal antibody epitope mapping\",\n      \"pmids\": [\"2777338\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No receptor for these epitopes yet identified\", \"Functional consequence of the epitope not established\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Showed that HLA-B allotypes carry defined peptide-binding motifs and that an α3-domain residue (Thr245) tunes CD8 co-receptor binding, linking polymorphism to both peptide selection and CD8 engagement.\",\n      \"evidence\": \"Transfection, pool peptide sequencing, in vitro CD8 binding, and T245A site-directed mutagenesis\",\n      \"pmids\": [\"9331948\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"CD8-binding effect characterized for a single allotype\", \"Physiological consequence of weak CD8 binding incompletely resolved\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Identified HLA-B as the specific ligand for the NK receptor KIR3DL1, establishing HLA-B's role in NK cell recognition beyond T cell antigen presentation.\",\n      \"evidence\": \"NK clonal cytotoxicity, HLA-allele transfection, and DX9 mAb blocking\",\n      \"pmids\": [\"8046332\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define which residues confer KIR3DL1 specificity\", \"Peptide-dependence of recognition not addressed\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Demonstrated that KIR3DL1/KIR3DS1 allotypes act epistatically with HLA-B Bw4 subtypes to modulate HIV/AIDS progression in a density- and binding-strength-dependent hierarchy, translating the molecular ligand relationship into in vivo immune control.\",\n      \"evidence\": \"Large-cohort genetic epistasis association studies of KIR and HLA-B subtypes in HIV-infected individuals\",\n      \"pmids\": [\"12134147\", \"17496894\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genetic association does not establish the molecular mechanism of NK activation at the cellular level\", \"Causal peptide contribution not yet tested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Showed that a single residue (position 116) controls peptide-loading efficiency, TAP binding, and maturation rate, linking fine allelic variation to trafficking kinetics and AIDS progression rate.\",\n      \"evidence\": \"Pulse-chase, TAP co-IP, peptide-binding and thermostability assays comparing HLA-B*3501 vs *3503\",\n      \"pmids\": [\"19838694\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Single allele pair from a single lab\", \"Direct in vivo link between trafficking kinetics and clinical outcome not proven\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Systematically defined polymorphic determinants of tapasin dependence and empty-form stability across 27 alleles, explaining why HLA-B allotypes differ in their assembly requirements.\",\n      \"evidence\": \"In vitro refolding, aggregation, and tapasin-deficient cell expression across 27 HLA-B alleles\",\n      \"pmids\": [\"24790147\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Single lab\", \"Precise structural mechanism of residue effects on tapasin engagement not crystallographically defined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Established TAP-independent assembly as a property of a subset of allotypes and connected it to resistance to viral TAP inhibitors, and revealed allele/cell-type-dependent surface expression and a non-canonical adhesion-amplifying role for empty HLA-B conformers.\",\n      \"evidence\": \"Expression of 27 alleles in TAP-deficient cells, peptide-binding and NK assays; primary-cell flow cytometry; tetramer/synapse imaging of empty HLA-B*35:01\",\n      \"pmids\": [\"29995954\", \"29989547\", \"29741477\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Generality of empty-conformer adhesion role across allotypes unknown\", \"In vivo relevance of TAP-independence to infection control not directly demonstrated\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrated peptide-dependence of NK recognition for HLA-B, including KIR3DS1 engagement of HLA-B*57:01 and KIR2DL3 recognition of a C1-epitope HLA-B*46:01 generated by intergenic mini-conversion, refining the rules of NK ligand formation.\",\n      \"evidence\": \"Defined-peptide KIR binding/NK functional assays; high-resolution immunopeptidomics with KIR2DL3 binding of peptide subsets\",\n      \"pmids\": [\"25740999\", \"28514659\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No crystal structures of these peptide-KIR complexes reported\", \"Quantitative contribution of peptide identity to NK activation in vivo unresolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined HLA-B as a relatively resistant target of viral immune evasion, with locus-specific resistance to HIV-1 Nef downregulation and HCMV US11-mediated ERAD, mapping the viral and host sequence determinants of differential targeting.\",\n      \"evidence\": \"Nef clone panel with site-directed mutagenesis and T cell recognition assays; US11 domain mutagenesis with peptidomics and co-IP\",\n      \"pmids\": [\"26787826\", \"31527904\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of HLA-B resistance to US11/Nef not fully resolved\", \"Whether resistance generalizes across all HLA-B allotypes untested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Established that HLA-B mediates drug hypersensitivity through direct, metabolism-independent drug binding within the peptide-binding groove and through peptide haptenation, identifying causal residues and demonstrating CD8+ T cell activation.\",\n      \"evidence\": \"SPR drug-HLA binding, mutagenesis, and CTL assays (carbamazepine/HLA-B*1502); transgenic mouse and immunopeptidomics (abacavir/flucloxacillin, HLA-B*57:01)\",\n      \"pmids\": [\"22322005\", \"29782330\", \"33633747\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Why specific allotypes confer hypersensitivity to specific drugs not fully predictable\", \"Role of CD4 help/costimulation thresholds in clinical reactions incompletely defined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Provided the structural and immunological basis for HLA-B*27-restricted autoimmunity, showing public BV9 TCRs cross-react with self and microbial peptides presented by HLA-B*27:05, and that disease-associated B*27 subtypes show elevated conformational dynamics.\",\n      \"evidence\": \"TCR isolation, yeast-display peptide libraries, peptide-MHC-TCR structures; crystallography with isotope-edited IR spectroscopy across B*27 subtypes; B27 immunopeptidomics\",\n      \"pmids\": [\"36477533\", \"26748477\", \"20112406\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Causal chain from molecular mimicry/dynamics to clinical disease not fully established\", \"No functional T cell validation in the immunopeptidomics dataset\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Implicated HLA-B in cancer-cell-intrinsic processes — cytokine-driven immunopeptidome remodeling, preferential sorting into extracellular vesicles, and modulation of ITGB1/migration — suggesting roles beyond classical antigen presentation.\",\n      \"evidence\": \"Immunopeptidomics under cytokine stimulation and in extracellular vesicles; HLA-B siRNA knockdown with migration and ITGB1 readouts in pancreatic cancer lines\",\n      \"pmids\": [\"30833945\", \"34211107\", \"32194036\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Migration effect is cell-line-dependent and mechanistically unclear\", \"Single-lab/single-cell-line observations not independently confirmed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How HLA-B nanoscale surface organization, allele-specific clustering, and the balance of canonical versus non-canonical (empty-conformer, vesicle-sorted) presentation integrate to set the threshold for T cell and NK cell activation remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying model linking surface clustering to functional output\", \"Allotype-by-cell-type rules for non-canonical presentation incomplete\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [6, 9, 11, 16, 29]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [1, 3, 23]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [5, 12, 16]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 2, 18, 23]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [2, 3, 9, 22]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [27]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 5, 7, 14, 22, 28]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [2, 3, 11, 19]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [7, 10, 21, 26, 28]}\n    ],\n    \"complexes\": [\n      \"MHC class I peptide-loading complex (heavy chain/β2-microglobulin/peptide)\"\n    ],\n    \"partners\": [\n      \"B2M\",\n      \"KIR3DL1\",\n      \"KIR3DS1\",\n      \"KIR2DL3\",\n      \"TAP1\",\n      \"TAP2\",\n      \"tapasin\",\n      \"CD8\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}