{"gene":"CD37","run_date":"2026-06-09T22:57:17","timeline":{"discoveries":[{"year":1988,"finding":"CD37 antigen (gp40-52) is a single-chain protein core of ~25 kDa with two N-linked complex carbohydrate chains comprising ~50% of total molecular mass; subcellular fractionation and electron microscopy showed it is associated with intracellular vesicles in addition to the cell surface, suggesting dual surface/cytoplasmic function.","method":"Biochemical analysis (immunoprecipitation, glycosidase treatment), electron microscopy, subcellular fractionation","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — direct biochemical characterization with EM localization, single lab, multiple orthogonal methods","pmids":["3257508"],"is_preprint":false},{"year":1989,"finding":"CD37 is a 244-amino acid protein lacking a conventional leader sequence, with an N-terminal cytoplasmic domain followed by three transmembrane sequences within the first 110 amino acids and a hydrophilic C-terminal region containing three N-glycosylation sites, establishing its topology as a four-transmembrane protein.","method":"cDNA cloning and sequence analysis, comparison with rat OX-44 NH2-terminal protein sequence","journal":"The Journal of experimental medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cDNA cloning with protein sequence validation, single lab, orthogonal protein and nucleotide approaches","pmids":["2466944"],"is_preprint":false},{"year":1993,"finding":"CD37 gene is located on human chromosome 19 (region 19p13–q13.4), distinct from paralogous tetraspanins CD53 (chr 1) and R2/C33 (chr 11).","method":"Human/rodent somatic cell hybrid panel mapping with human-specific probes and deletion hybrid regional assignment","journal":"Immunogenetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — standard chromosomal mapping using somatic cell hybrids, single lab","pmids":["8436422"],"is_preprint":false},{"year":1994,"finding":"CD37 co-precipitates with MHC class II (DR) glycoproteins as part of large multicomponent membrane complexes also containing CD53, TAPA-1, R2/C33, CD19, and CD21 in B cells, indicating CD37 resides in tetraspanin-enriched microdomains physically associated with MHC class II.","method":"Co-immunoprecipitation and preclearing experiments from mild detergent lysates of human B-cell lines and tonsillar B cells","journal":"Immunogenetics","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — reciprocal co-precipitation in multiple cell types, single lab, single method (co-IP)","pmids":["8119731"],"is_preprint":false},{"year":2000,"finding":"CD37-deficient mice show selectively impaired T-cell-dependent IgG1 antibody responses (reduced serum IgG1, poor responses to antigen without adjuvant and to viral infections), demonstrating a role for CD37 in T cell–B cell interactions under suboptimal costimulatory conditions; lymphoid organ development was normal.","method":"Targeted gene inactivation (knockout mice), immunization experiments, serum immunoglobulin measurement, flow cytometry","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO model with defined humoral immune phenotype, multiple immunization conditions tested, replicated across immune challenges","pmids":["10891477"],"is_preprint":false},{"year":2004,"finding":"CD37 negatively regulates T cell proliferation by modulating early TCR signaling: CD37-deficient T cells are hyperproliferative with enhanced IL-2 production and increased CD4/CD8-associated p56Lck kinase activity; cross-linking CD37 on human T cells inhibited CD3-induced proliferation.","method":"CD37 knockout mice, MLR, Con A and anti-CD3 stimulation assays, division cycle analysis, p56Lck kinase activity assay, CD37 cross-linking on human T cells","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO mouse phenotype replicated across multiple stimulation conditions, biochemical kinase activity measurement, and human T cell cross-linking functional assay","pmids":["14978098"],"is_preprint":false},{"year":2007,"finding":"Dectin-1 functionally interacts with tetraspanin CD37 on APC surfaces; CD37 stabilizes dectin-1 at the plasma membrane by preventing its internalization, and CD37 deficiency results in a 10-fold increase in dectin-1-induced IL-6 production in macrophages despite reduced surface dectin-1 levels.","method":"CD37-/- mice, confocal colocalization, dectin-1 internalization assay, transfection of CD37 into macrophage cell line, cytokine measurement after curdlan (specific dectin-1 ligand) stimulation","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO macrophages, CD37 transfection rescue, ligand-specific stimulation, multiple orthogonal methods in one study","pmids":["17182550"],"is_preprint":false},{"year":2009,"finding":"CD37 inhibits IgA immune responses in vivo; CD37-deficient mice show 15-fold elevated serum IgA and increased IgA+ plasma cells in spleen, MALT, and bone marrow. This was directly attributable to CD37 deficiency on B cells (shown by bone marrow chimeras). Mechanistically, CD37 deficiency elevates germinal center IL-6, and neutralizing IL-6 in vivo reverses the increased IgA response.","method":"CD37-/- mice, bone marrow chimeric mice, in vivo IL-6 neutralization, immunization, serum Ig measurement, ELISPOT","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — bone marrow chimeras establish B cell-intrinsic mechanism, IL-6 neutralization rescue provides causal pathway placement, multiple orthogonal methods","pmids":["19282981"],"is_preprint":false},{"year":2009,"finding":"CD37 and CD151 differentially regulate dendritic cell function: CD37-deficient DCs are hyper-stimulatory to T cells through enhanced peptide/MHC presentation, while CD151 controls co-stimulation, demonstrating that CD37 restrains antigen presentation by DCs.","method":"CD37-/- and CD151-/- mouse DC functional assays, peptide/MHC presentation to antigen-specific T cells, T cell activation readouts","journal":"European journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — two parallel KO models tested, antigen-specific T cell readout, dissection of two distinct mechanisms in one study","pmids":["19089816"],"is_preprint":false},{"year":2012,"finding":"CD37 directly mediates signal transduction upon ligation: it becomes tyrosine phosphorylated and associates with proximal signaling molecules. Two functionally opposing tyrosine residues were identified: a Y in the N-terminal 'ITIM-like' motif mediates SHP1-dependent apoptotic signaling, while a Y in the C-terminal 'ITAM motif' mediates PI3K-dependent survival signaling.","method":"CD37 ligation with bivalent SMIP molecule, phosphotyrosine immunoprecipitation, mutagenesis of ITIM/ITAM tyrosine residues, SHP1 and PI3K pathway assays, apoptosis assays","journal":"Cancer cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — active-site mutagenesis identifying specific tyrosine residues with opposing functions, biochemical pathway characterization, direct signaling assays","pmids":["22624718"],"is_preprint":false},{"year":2012,"finding":"CD37 is required for α4β1 integrin-dependent Akt survival signaling in IgG-secreting plasma cells: CD37-deficient plasma cells show impaired α4β1 integrin mobility and clustering in the plasma membrane upon VCAM-1 binding, leading to defective downstream Akt activation, increased apoptosis in germinal centers, and reduced numbers of long-lived plasma cells.","method":"CD37-/- mice, flow cytometry of plasma cell populations, apoptosis assays, integrin mobility/clustering assays, Akt phosphorylation assays, bone marrow immunoglobulin secretion quantification","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO mouse model with defined cellular phenotype, mechanistic dissection of integrin clustering and Akt pathway, multiple orthogonal methods","pmids":["23150881"],"is_preprint":false},{"year":2013,"finding":"CD37 ablation impairs dendritic cell migration from skin to draining lymph nodes, chemotactic migration, integrin-mediated adhesion under flow, cell spreading and actin protrusion formation, and in vivo priming of naive T cells; multiphoton microscopy showed reduced migration rate and increased randomness of DC movement in CD37-/- mice.","method":"CD37-/- mice, in vivo DC migration assays (skin painting), multiphoton microscopy, flow chamber adhesion assay, chemotaxis assay, adoptive T cell transfer priming assay","journal":"European journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple in vivo and in vitro migration assays in KO mice, live imaging, multiple mechanistic readouts","pmids":["23420539"],"is_preprint":false},{"year":2016,"finding":"CD37 directly interacts with SOCS3 (suppressor of cytokine signaling 3); CD37 deficiency drives constitutive activation of the IL-6 signaling pathway. CD37-/- mice develop germinal center-derived B cell lymphoma, and double Cd37/Il6 knockout mice are fully protected from lymphoma, placing CD37 upstream of IL-6 signaling as a tumor suppressor.","method":"CD37-/- mice, co-immunoprecipitation (CD37–SOCS3 interaction), double Cd37/Il6 knockout mice, IL-6 pathway activation assays, lymphoma incidence scoring","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis via double KO fully rescuing lymphoma phenotype, direct biochemical interaction identified by co-IP, causal pathway confirmed","pmids":["26784544"],"is_preprint":false},{"year":2016,"finding":"CD37 and CD82 have opposing roles in DC biology via differential activation of small GTPases: CD37 promotes activation of Rac-1 to support cell spreading and migration, while CD82 negatively regulates RhoA; both tetraspanins negatively regulate Cdc42. CD37 ablation impairs actin protrusions and cell spreading on fibronectin.","method":"CD37-/- and CD82-/- BMDC functional assays, small GTPase activity assays (Rac-1, RhoA, Cdc42), cell spreading and migration assays, MHC class II maturation assays","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — two parallel KO models, direct GTPase activity measurements, multiple orthogonal functional readouts","pmids":["26729805"],"is_preprint":false},{"year":2015,"finding":"CD37 regulates β2 integrin-mediated neutrophil adhesion and migration: CD37-/- neutrophils show impaired adhesion to ICAM-1 despite normal high-affinity β2 integrin display, impaired actin polymerization, reduced cell spreading and polarization, dysregulated Rac-1 activation, and accelerated β2 integrin internalization. Superresolution microscopy showed CD37 and CD18 do not significantly co-cluster, indicating CD37 acts downstream of integrin engagement on cytoskeletal function rather than via direct integrin interaction.","method":"CD37-/- mice, intravital microscopy, in vitro flow chamber adhesion assay, superresolution microscopy, Rac-1 activation assay, actin polymerization assay, integrin internalization assay","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO mouse in vivo and in vitro, superresolution imaging rules out direct molecular interaction, Rac-1 biochemical assay, multiple orthogonal methods","pmids":["26566675"],"is_preprint":false},{"year":2018,"finding":"CLEC-2-dependent DC migration is controlled by CD37: CD37 specifically interacts with CLEC-2; Cd37-/- DCs show reduced surface CLEC-2, impaired adhesion and migration on lymph node stromal cells, failure to form actin protrusions upon podoplanin-induced CLEC-2 stimulation, and failure to inhibit actomyosin contractility in stromal cells. CD37 is required for CLEC-2 recruitment to its ligand podoplanin in the membrane.","method":"Co-immunoprecipitation (CD37–CLEC-2 interaction), Cd37-/- DCs, microcontact printing, 3D collagen matrix migration assay, CLEC-2 internalization/surface expression measurement","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct biochemical interaction shown by co-IP, KO phenotyping, microcontact printing for membrane recruitment, multiple orthogonal assays","pmids":["30185523"],"is_preprint":false},{"year":2018,"finding":"IL-6 is essential for glomerular IgA deposition and renal pathology in CD37-deficient mice: Cd37-/-/Il6-/- double-knockout mice show no glomerular IgA deposition and are protected from exacerbated renal failure, establishing that CD37 normally suppresses IgA nephropathy-like disease by inhibiting the IL-6 pathway.","method":"Cd37-/- mice, Cd37/Il6 double-knockout mice, anti-GBM nephritis induction, serum IL-6 measurement, immunofluorescence for IgA deposition, histopathology","journal":"Kidney international","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis via double KO fully rescuing pathology, LPS challenge model, multiple pathological readouts","pmids":["29551516"],"is_preprint":false},{"year":2022,"finding":"CD37 acts as an inhibitor of fatty acid (FA) metabolism in lymphoma by directly interacting with the FA transporter FATP1; deletion of CD37 increases FA oxidation and uptake of exogenous palmitate into energy and membrane building blocks, a phenotype reversed by FATP1 inhibition.","method":"CD37 knockout lymphoma cells, co-immunoprecipitation (CD37–FATP1 interaction), functional FA oxidation assays, metabolomics, serum palmitate depletion in mouse studies, FATP1 inhibitor rescue experiments, patient lymphoma tissue lipid staining","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct protein–protein interaction by co-IP, functional rescue by FATP1 inhibition, metabolomics, in vivo mouse data, patient tissue confirmation","pmids":["36100608"],"is_preprint":false},{"year":2022,"finding":"IRF8 is a transcriptional activator of CD37 expression in DLBCL: IRF8 directly binds the CD37 promoter (confirmed by DNA pulldown/MS and ChIP), IRF8 overexpression increases CD37 protein levels, and CRISPR/Cas9 knockout of IRF8 decreases CD37 levels in DLBCL cell lines. CD37-negative DLBCL specifically lacks CD37 promoter activity independent of promoter DNA methylation.","method":"Quantitative nuclear proteomics, DNA pulldown + mass spectrometry, targeted ChIP, CRISPR/Cas9 IRF8 knockout, IRF8 overexpression, promoter methylation analysis, IHC (n=206 primary DLBCL)","journal":"Blood advances","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — direct promoter binding by ChIP and DNA pulldown-MS, loss-of-function and gain-of-function in multiple cell lines, large patient cohort validation","pmids":["35086136"],"is_preprint":false},{"year":2023,"finding":"N-glycosylation of CD37 is required for its surface expression: glycosylation mutants of CD37 show impaired cell surface localization. Glycosylation affects CD37 interaction with partner proteins CD53 and CD20 in a localization-dependent manner, but CD37 interaction with IL-6Rα is glycosylation-independent.","method":"Generation of CD37 glycosylation mutants, flow cytometry for surface expression, dSTORM single-molecule superresolution microscopy for nanoscale membrane organization, co-immunoprecipitation for partner protein interactions","journal":"Biophysical journal","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — mutagenesis of glycosylation sites, superresolution imaging, co-IP for multiple partner interactions, single lab but multiple orthogonal methods","pmids":["38031400"],"is_preprint":false},{"year":2024,"finding":"CD37 forms a complex with CD20, and CD20 stabilizes CD37 in the cell membrane; CD20 knockout cells show major downregulation of CD37, increased CD37 internalization rate, and reduced efficacy of anti-CD37 complement-dependent cytotoxicity that is partially restored by lysosome inhibition.","method":"CD20 knockout cell lines, co-immunoprecipitation (CD20–CD37 complex), flow cytometry for surface CD37, internalization assay, CDC assay, lysosome inhibitor rescue","journal":"Oncoimmunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct complex shown by co-IP, KO functional rescue, single lab, multiple orthogonal methods","pmids":["38846084"],"is_preprint":false},{"year":2024,"finding":"CD37 interacts with integrin α4β7 in AML cells and activates the PI3K-AKT pathway mediated by integrin signaling; CD37 knockdown in AML retards proliferation and increases apoptosis, and CD37 deficiency in vivo impairs leukemia maintenance and LSC self-renewal (serial transplantation) without affecting normal hematopoiesis.","method":"Co-immunoprecipitation (CD37–integrin α4β7), CD37 knockdown in human AML cell lines, CD37-deficient mouse AML model, serial transplantation assay, PI3K-AKT phosphorylation assays, colony formation assay","journal":"Stem cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct protein interaction by co-IP, in vivo KO model, signaling pathway measurement, single lab","pmids":["40250439"],"is_preprint":false},{"year":2024,"finding":"CD37 acts as a phagocytic checkpoint in macrophages: tumorous macrophage migration inhibitory factor (MIF) directly binds CD37, promoting phosphorylation of CD37 Y13 and activating a signaling cascade involving SHP1 recruitment and AKT inhibition that impairs phagocytosis. Targeting CD37 with an antibody promotes phagocytosis of multiple cancer cell types in vitro and tumor clearance in vivo.","method":"In vitro phagocytosis assays, ribosome profiling of sorted macrophages, direct binding assay (MIF–CD37), CD37 Y13 phosphorylation measurement, SHP1 recruitment assay, AKT signaling assay, CD37 KO macrophages, in vivo preclinical mouse tumor models","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — direct protein–protein binding established, site-specific phosphorylation identified, downstream signaling cascade characterized, in vitro reconstitution + in vivo multiple tumor models","pmids":["40675974"],"is_preprint":false},{"year":2024,"finding":"CD37 is in close proximity to the BCR in B cells; CRISPR knockout of CD37 heightens BCR signaling, slows BCR endocytosis, and reduces peptide-MHC class II complex formation, demonstrating that CD37 modulates BCR function at the membrane.","method":"Proximity-based biotinylation (BioID) + mass spectrometry, CRISPR/Cas9 CD37 knockout in B cell line, BCR signaling assay, BCR endocytosis assay, peptide-MHC class II presentation assay","journal":"ImmunoHorizons","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proximity labeling identifies BCR association, CRISPR KO with three functional readouts, single lab","pmids":["38625120"],"is_preprint":false},{"year":2025,"finding":"CD37 positively regulates platelet activation and thrombosis: Cd37-/- platelets exhibit impaired integrin αIIbβ3 signaling (reduced fibrinogen spreading and agonist-induced αIIbβ3 activation); chimeric mice reconstituted with Cd37-/- bone marrow showed significantly increased time to vessel occlusion in the FeCl3 carotid artery thrombosis model, without effects on hemostasis.","method":"Cd37-/- mice, bone marrow chimera thrombosis model (FeCl3 carotid artery), platelet aggregation assays, integrin αIIbβ3 activation assay, fibrinogen spreading assay, coagulation metrics, RNA-sequencing of human and mouse platelets","journal":"Cardiovascular research","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO mouse in vivo thrombosis model, bone marrow chimeras establish cell-autonomous platelet function, biochemical integrin signaling assays, human and mouse data","pmids":["40126944"],"is_preprint":false},{"year":2025,"finding":"DuoHexaBody-CD37 induces direct cytotoxicity in DLBCL by inducing CD37 clustering at the cell surface (without internalization) and predominantly upregulating p-SHP1(Y564) in DLBCL cells. In primary B cells, the same antibody activates p-AKT(S473) and MAPK survival signaling. The N-terminus of CD37 is required for DuoHexaBody-CD37-induced signaling, established using CD37 N-terminal mutants.","method":"Unbiased phosphoproteomic screening (26 phosphoproteins), CD37 clustering imaging, CD37 N-terminal mutants, p-SHP1 and p-AKT signaling assays, cytotoxicity assays in DLBCL cell lines and primary B cells","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phosphoproteomics with site-specific readouts, N-terminal mutagenesis establishes domain requirement, preprint not yet peer-reviewed","pmids":[],"is_preprint":true}],"current_model":"CD37 is a four-transmembrane tetraspanin glycoprotein that functions as a direct signal transducer and membrane organizer in B cells, T cells, dendritic cells, neutrophils, and platelets: upon ligation it undergoes tyrosine phosphorylation at opposing ITIM-like (N-terminal, Y13/SHP1-dependent pro-apoptotic) and ITAM-like (C-terminal, PI3K-dependent pro-survival) motifs; it scaffolds α4β1 and α4β7 integrins in the plasma membrane to sustain Akt survival signaling; it stabilizes partner receptors (dectin-1, CLEC-2) at the cell surface and thereby controls downstream IL-6 production and DC migration via Rac-1 activation; it directly suppresses fatty acid uptake by inhibiting FATP1; it interacts with SOCS3 to restrain constitutive IL-6 signaling and lymphomagenesis; it modulates BCR endocytosis and antigen presentation; in macrophages it receives MIF-driven phosphorylation at Y13 to recruit SHP1 and inhibit AKT, acting as a phagocytic checkpoint; and its expression is transcriptionally activated by IRF8 and stabilized at the membrane by its complex partner CD20."},"narrative":{"mechanistic_narrative":"CD37 is a four-transmembrane tetraspanin glycoprotein that functions as a membrane organizer and bidirectional signal transducer in immune cells, platelets, and macrophages, controlling humoral immunity, cell migration, and survival signaling [PMID:2466944, PMID:22624718]. It resides within tetraspanin-enriched membrane microdomains physically associated with MHC class II and other tetraspanins and B-cell coreceptors [PMID:8119731], and its N-glycosylation is required for surface delivery and for governing interactions with partner proteins including CD53 and CD20 [PMID:38031400]. Upon ligation CD37 is tyrosine phosphorylated on two functionally opposing motifs: an N-terminal ITIM-like tyrosine that recruits SHP1 to drive apoptotic signaling and a C-terminal ITAM-like tyrosine that engages PI3K for survival signaling [PMID:22624718]. CD37 organizes and stabilizes partner receptors at the membrane—it prevents internalization of dectin-1 and recruits CLEC-2 to its ligand podoplanin—and these activities, together with Rac-1 activation and integrin-dependent adhesion, drive dendritic-cell spreading and migration [PMID:17182550, PMID:30185523, PMID:26729805]. Through its restraint of IL-6 signaling, in part via direct interaction with SOCS3, CD37 suppresses IgA responses, IgA nephropathy-like renal pathology, and germinal-center-derived B-cell lymphoma, with double Cd37/Il6 knockout fully reversing lymphoma and renal disease [PMID:26784544, PMID:19282981, PMID:29551516]. In malignancy CD37 also engages α4 integrins to sustain Akt survival signaling in plasma cells and AML, suppresses fatty-acid uptake by inhibiting FATP1, and acts as a macrophage phagocytic checkpoint when MIF binding triggers Y13 phosphorylation, SHP1 recruitment, and AKT inhibition [PMID:23150881, PMID:36100608, PMID:40250439, PMID:40675974]. CD37 expression is transcriptionally activated by IRF8 binding the CD37 promoter [PMID:35086136], and its surface stability is reinforced by complex formation with CD20 [PMID:38846084].","teleology":[{"year":1989,"claim":"Defining CD37's primary structure and membrane topology established it as a four-transmembrane tetraspanin, providing the structural framework for all later functional work.","evidence":"cDNA cloning and sequence analysis with rat OX-44 protein sequence comparison","pmids":["2466944"],"confidence":"Medium","gaps":["No high-resolution structure","Functional role of individual domains not yet defined at this stage"]},{"year":1994,"claim":"Showing CD37 co-precipitates with MHC class II and other tetraspanins and B-cell coreceptors placed it within tetraspanin-enriched membrane microdomains, framing it as a membrane organizer rather than a solitary receptor.","evidence":"Reciprocal co-immunoprecipitation from mild detergent lysates of human B cells","pmids":["8119731"],"confidence":"Medium","gaps":["Stoichiometry and direct versus indirect contacts within the complex unresolved","Functional consequence of MHC II association not tested"]},{"year":2004,"claim":"Knockout phenotyping revealed CD37 as a negative regulator of immune cell activation, showing impaired T-cell-dependent IgG1 responses yet hyperproliferative T cells with elevated p56Lck activity.","evidence":"CD37 knockout mice, immunization, MLR/anti-CD3 stimulation, p56Lck kinase assay, human T-cell cross-linking","pmids":["10891477","14978098"],"confidence":"High","gaps":["Molecular link between CD37 and Lck regulation not defined","Mechanism of selective IgG1 defect unexplained"]},{"year":2009,"claim":"Parallel studies established CD37 as a restraint on antigen-presenting cell function and IgA responses, with bone marrow chimeras and IL-6 neutralization pinpointing a B-cell-intrinsic, IL-6-dependent mechanism.","evidence":"CD37-/- and CD151-/- DC presentation assays; bone marrow chimeras and in vivo IL-6 neutralization","pmids":["19089816","19282981","17182550"],"confidence":"High","gaps":["How CD37 loss elevates IL-6 not yet mechanistically explained at this stage","Receptor partners mediating presentation restraint partly unknown"]},{"year":2012,"claim":"Identification of opposing N-terminal ITIM-like (SHP1/pro-apoptotic) and C-terminal ITAM-like (PI3K/pro-survival) tyrosine motifs established CD37 as a direct bidirectional signal transducer, and integrin/Akt work tied it to plasma-cell survival.","evidence":"SMIP ligation, phosphotyrosine IP, ITIM/ITAM tyrosine mutagenesis; KO plasma-cell integrin clustering and Akt assays","pmids":["22624718","23150881"],"confidence":"High","gaps":["Kinases phosphorylating each motif not defined","Switch determining ITIM versus ITAM engagement unresolved"]},{"year":2013,"claim":"Linking CD37 to Rac-1 activation, actin protrusion, integrin adhesion and dendritic-cell migration defined its cytoskeletal-regulatory role in immune cell motility.","evidence":"CD37-/- DC in vivo migration, multiphoton imaging, flow adhesion, chemotaxis, and GTPase activity assays (CD37 vs CD82)","pmids":["23420539","26729805"],"confidence":"High","gaps":["Direct effector linking CD37 to Rac-1 unknown","Whether GTPase regulation is via partner receptors not resolved"]},{"year":2016,"claim":"Discovery of CD37–SOCS3 interaction and Cd37/Il6 double-knockout rescue placed CD37 upstream of IL-6 signaling as a tumor suppressor whose loss drives germinal-center B-cell lymphoma.","evidence":"CD37-/- mice, CD37–SOCS3 co-IP, double Cd37/Il6 KO epistasis, lymphoma scoring","pmids":["26784544"],"confidence":"High","gaps":["Biochemical basis of SOCS3-mediated IL-6 restraint not fully resolved","Contribution of cell-extrinsic IL-6 sources unclear"]},{"year":2018,"claim":"CD37 was shown to stabilize and recruit the partner receptor CLEC-2 to podoplanin to drive DC migration, and to suppress IL-6-dependent IgA nephropathy-like renal disease, generalizing its receptor-organizing and IL-6-restraining functions.","evidence":"CD37–CLEC-2 co-IP, microcontact printing, 3D migration; Cd37/Il6 double KO anti-GBM nephritis model","pmids":["30185523","29551516"],"confidence":"High","gaps":["Structural basis of CLEC-2 recruitment unknown","How CD37 simultaneously stabilizes diverse partner receptors not unified"]},{"year":2022,"claim":"CD37 was identified as a direct inhibitor of fatty-acid metabolism via FATP1 and as a transcriptional target of IRF8, connecting membrane CD37 to lymphoma metabolism and to the upstream control of its own expression.","evidence":"CD37–FATP1 co-IP, FA oxidation/metabolomics, FATP1 inhibitor rescue; IRF8 ChIP/DNA pulldown-MS, IRF8 KO/overexpression, DLBCL cohort","pmids":["36100608","35086136"],"confidence":"High","gaps":["Mechanism by which CD37 inhibits FATP1 transport activity not defined","Other transcriptional regulators of CD37 not surveyed"]},{"year":2024,"claim":"Multiple studies extended CD37's role to integrin-driven AKT survival in AML, BCR modulation in B cells, CD20-dependent membrane stabilization, and a MIF-triggered Y13/SHP1 phagocytic checkpoint in macrophages, unifying it as a membrane scaffold controlling survival and effector signaling.","evidence":"CD37–α4β7 co-IP and AML KO model; BioID BCR proximity and CRISPR KO; CD20 KO complex/internalization assays; MIF–CD37 binding, Y13 phosphorylation, SHP1/AKT and phagocytosis assays","pmids":["40250439","38625120","38846084","40675974"],"confidence":"Medium","gaps":["Whether α4β7 and α4β1 use shared signaling machinery unresolved","Direct MIF–CD37 binding interface not structurally defined","CD20 dependence of CD37 stability across cell types not generalized"]},{"year":2025,"claim":"Platelet studies revealed CD37 as a positive regulator of αIIbβ3 integrin signaling and thrombosis, broadening its integrin-organizing function beyond immune cells, while antibody-clustering studies refined the N-terminal requirement for SHP1-biased signaling.","evidence":"Cd37-/- platelet aggregation, αIIbβ3 activation and FeCl3 thrombosis chimeras; DuoHexaBody-CD37 clustering, phosphoproteomics and N-terminal mutants (preprint)","pmids":["40126944"],"confidence":"High","gaps":["Mechanism coupling CD37 to platelet integrin inside-out/outside-in signaling unknown","Cell-type basis for opposing positive vs negative integrin effects unresolved"]},{"year":null,"claim":"How CD37 mechanistically switches between its opposing ITIM/SHP1 and ITAM/PI3K outputs and coordinates its many partner receptors across distinct cell types remains the central unresolved question.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of CD37 in complex with any partner","Kinases and adaptors selecting ITIM versus ITAM signaling unidentified","Determinants of context-dependent positive versus negative integrin regulation unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[9,22,25]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[6,12,15,17,20]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[9,10,21]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[3,19]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1,3,19]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[4,5,7,8,23]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[9,10,21,22]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[12,16,17,22]},{"term_id":"R-HSA-109582","term_label":"Hemostasis","supporting_discovery_ids":[24]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[17]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[18]}],"complexes":["tetraspanin-enriched microdomain (with MHC class II, CD53, TAPA-1, CD19, CD21)","CD37–CD20 complex"],"partners":["SOCS3","CLEC-2","FATP1","CD20","CD53","ITGA4","MIF","IL6R"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P11049","full_name":"Leukocyte antigen CD37","aliases":["Tetraspanin-26","Tspan-26"],"length_aa":281,"mass_kda":31.7,"function":"Structural component of specialized membrane microdomains known as tetraspanin-enriched microdomains (TERMs), which act as platforms for receptor clustering and signaling. Participates thereby in diverse biological functions such as cell signal transduction, adhesion, migration and protein trafficking (PubMed:22624718). Upon ligand binding, two signaling pathways are activated, one acting through phosphorylation by LYN leading to cell death or a survival pathway with activation of GSK3B (PubMed:22624718). Plays an essential role essential for clustering of integrin ITGA4/ITGB1 and promotes its mobility in the plasma membrane of B-cells. In turn, participates in ITGA4/ITGB1 integrin-mediated antiapoptotic signaling through AKT (By similarity). Also plays a role in the migration of dendritic cells and neutrophils to draining lymph nodes, as well as in their integrin-mediated adhesion (By similarity). Negatively regulates IL-6 responses through direct interaction with SOCS3 thereby preventing constitutive IL-6 signaling (PubMed:26784544). Alternatively, inhibition of IL-6 signaling can also occur via interaction and stabilization of DECTIN1/CLEC7A at the cell membrane to inhibit its ability to promote the production of IL-6 (PubMed:17182550)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/P11049/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CD37","classification":"Not Classified","n_dependent_lines":9,"n_total_lines":1208,"dependency_fraction":0.0074503311258278145},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CD37","total_profiled":1310},"omim":[{"mim_id":"614406","title":"SLP ADAPTOR- AND CSK-INTERACTING MEMBRANE PROTEIN; SCIMP","url":"https://www.omim.org/entry/614406"},{"mim_id":"602380","title":"UROPLAKIN 1B; UPK1B","url":"https://www.omim.org/entry/602380"},{"mim_id":"600769","title":"TETRASPANIN 8; TSPAN8","url":"https://www.omim.org/entry/600769"},{"mim_id":"600623","title":"CD82 ANTIGEN; CD82","url":"https://www.omim.org/entry/600623"},{"mim_id":"186845","title":"CD81 ANTIGEN; CD81","url":"https://www.omim.org/entry/186845"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Golgi apparatus","reliability":"Approved"},{"location":"Plasma membrane","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"bone marrow","ntpm":146.8},{"tissue":"intestine","ntpm":112.2},{"tissue":"lymphoid tissue","ntpm":233.1}],"url":"https://www.proteinatlas.org/search/CD37"},"hgnc":{"alias_symbol":["TSPAN26"],"prev_symbol":[]},"alphafold":{"accession":"P11049","domains":[{"cath_id":"-","chopping":"4-118_241-281","consensus_level":"high","plddt":89.5144,"start":4,"end":281}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P11049","model_url":"https://alphafold.ebi.ac.uk/files/AF-P11049-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P11049-F1-predicted_aligned_error_v6.png","plddt_mean":83.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CD37","jax_strain_url":"https://www.jax.org/strain/search?query=CD37"},"sequence":{"accession":"P11049","fasta_url":"https://rest.uniprot.org/uniprotkb/P11049.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P11049/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P11049"}},"corpus_meta":[{"pmid":"8119731","id":"PMC_8119731","title":"Association of four antigens of the tetraspans family (CD37, CD53, TAPA-1, and R2/C33) with MHC class II glycoproteins.","date":"1994","source":"Immunogenetics","url":"https://pubmed.ncbi.nlm.nih.gov/8119731","citation_count":166,"is_preprint":false},{"pmid":"1403053","id":"PMC_1403053","title":"Imaging, dosimetry, and radioimmunotherapy with iodine 131-labeled anti-CD37 antibody in B-cell lymphoma.","date":"1992","source":"Journal of clinical oncology : official journal of the American Society of Clinical Oncology","url":"https://pubmed.ncbi.nlm.nih.gov/1403053","citation_count":139,"is_preprint":false},{"pmid":"30089630","id":"PMC_30089630","title":"Anti-CD37 chimeric antigen receptor T cells are active against B- and T-cell lymphomas.","date":"2018","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/30089630","citation_count":119,"is_preprint":false},{"pmid":"1401919","id":"PMC_1401919","title":"C33 antigen recognized by monoclonal antibodies inhibitory to human T cell leukemia virus type 1-induced syncytium formation is a member of a new family of transmembrane proteins including CD9, CD37, CD53, and CD63.","date":"1992","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/1401919","citation_count":115,"is_preprint":false},{"pmid":"22624718","id":"PMC_22624718","title":"Tetraspanin CD37 directly mediates transduction of survival and apoptotic signals.","date":"2012","source":"Cancer cell","url":"https://pubmed.ncbi.nlm.nih.gov/22624718","citation_count":114,"is_preprint":false},{"pmid":"17440052","id":"PMC_17440052","title":"Targeting CD37-positive lymphoid malignancies with a novel engineered small modular immunopharmaceutical.","date":"2007","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/17440052","citation_count":112,"is_preprint":false},{"pmid":"14978098","id":"PMC_14978098","title":"A regulatory role for CD37 in T cell proliferation.","date":"2004","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/14978098","citation_count":104,"is_preprint":false},{"pmid":"2466944","id":"PMC_2466944","title":"The primary structure of the human leukocyte antigen CD37, a species homologue of the rat MRC OX-44 antigen.","date":"1989","source":"The Journal of experimental medicine","url":"https://pubmed.ncbi.nlm.nih.gov/2466944","citation_count":103,"is_preprint":false},{"pmid":"3257508","id":"PMC_3257508","title":"The B cell-associated CD37 antigen (gp40-52). 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1990)","url":"https://pubmed.ncbi.nlm.nih.gov/25154027","citation_count":10,"is_preprint":false},{"pmid":"33683501","id":"PMC_33683501","title":"A phase Ib, open label, dose escalation trial of the anti-CD37 monoclonal antibody, BI 836826, in combination with ibrutinib in patients with relapsed/refractory chronic lymphocytic leukemia.","date":"2021","source":"Investigational new drugs","url":"https://pubmed.ncbi.nlm.nih.gov/33683501","citation_count":10,"is_preprint":false},{"pmid":"38846084","id":"PMC_38846084","title":"CD20 expression regulates CD37 levels in B-cell lymphoma - implications for immunotherapies.","date":"2024","source":"Oncoimmunology","url":"https://pubmed.ncbi.nlm.nih.gov/38846084","citation_count":9,"is_preprint":false},{"pmid":"35171311","id":"PMC_35171311","title":"CD37 expression in follicular lymphoma.","date":"2022","source":"Annals of 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loss cause resistance to naratuximab emtansine in lymphomas.","date":"2024","source":"Blood advances","url":"https://pubmed.ncbi.nlm.nih.gov/39374583","citation_count":5,"is_preprint":false},{"pmid":"33523334","id":"PMC_33523334","title":"A phase Ib, open-label, dose-escalation trial of the anti-CD37 monoclonal antibody, BI 836826, in combination with gemcitabine and oxaliplatin in patients with relapsed/refractory diffuse large B-cell lymphoma.","date":"2021","source":"Investigational new drugs","url":"https://pubmed.ncbi.nlm.nih.gov/33523334","citation_count":5,"is_preprint":false},{"pmid":"40675974","id":"PMC_40675974","title":"Targeting CD37 promotes macrophage-dependent phagocytosis of multiple cancer cell types and facilitates tumor clearance in mice.","date":"2025","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/40675974","citation_count":4,"is_preprint":false},{"pmid":"40126944","id":"PMC_40126944","title":"Tetraspanin CD37 regulates platelet hyperreactivity and thrombosis.","date":"2025","source":"Cardiovascular research","url":"https://pubmed.ncbi.nlm.nih.gov/40126944","citation_count":4,"is_preprint":false},{"pmid":"38014209","id":"PMC_38014209","title":"PI3Kδ activation, IL6 over-expression, and CD37 loss cause resistance to the targeting of CD37-positive lymphomas with the antibody-drug conjugate naratuximab emtansine.","date":"2023","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/38014209","citation_count":4,"is_preprint":false},{"pmid":"29029255","id":"PMC_29029255","title":"Plasmids can transfer to Clostridium difficile CD37 and 630Δerm both by a DNase resistant conjugation-like mechanism and a DNase sensitive mechanism.","date":"2017","source":"FEMS microbiology letters","url":"https://pubmed.ncbi.nlm.nih.gov/29029255","citation_count":4,"is_preprint":false},{"pmid":"40250439","id":"PMC_40250439","title":"CD37 regulates the self-renewal of leukemic stem cells via integrin-mediated signaling in acute myeloid leukemia.","date":"2025","source":"Stem cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/40250439","citation_count":3,"is_preprint":false},{"pmid":"40739330","id":"PMC_40739330","title":"Combining MCL-1 inhibition and CD37-directed chimeric antigen receptor T cells as an effective strategy to target T-cell lymphoma.","date":"2025","source":"Leukemia","url":"https://pubmed.ncbi.nlm.nih.gov/40739330","citation_count":3,"is_preprint":false},{"pmid":"35486574","id":"PMC_35486574","title":"Anti-CD37 radioimmunotherapy with 177Lu-NNV003 synergizes with the PARP inhibitor olaparib in treatment of non-Hodgkin's lymphoma in vitro.","date":"2022","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/35486574","citation_count":3,"is_preprint":false},{"pmid":"24235129","id":"PMC_24235129","title":"In the spotlight: a novel CD37 antibody-drug conjugate.","date":"2013","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/24235129","citation_count":3,"is_preprint":false},{"pmid":"38625120","id":"PMC_38625120","title":"Proximity-Based Labeling Identifies MHC Class II and CD37 as B Cell Receptor-Proximal Proteins with Immunological Functions.","date":"2024","source":"ImmunoHorizons","url":"https://pubmed.ncbi.nlm.nih.gov/38625120","citation_count":2,"is_preprint":false},{"pmid":"24989269","id":"PMC_24989269","title":"[Significance of CD37 expression in malignant B cells].","date":"2014","source":"Zhongguo shi yan xue ye xue za zhi","url":"https://pubmed.ncbi.nlm.nih.gov/24989269","citation_count":2,"is_preprint":false},{"pmid":"37274903","id":"PMC_37274903","title":"The Impact of CD37 Ectoenzyme Expression in Benign and Malignant Colorectal Tumors.","date":"2022","source":"Archives of Razi Institute","url":"https://pubmed.ncbi.nlm.nih.gov/37274903","citation_count":1,"is_preprint":false},{"pmid":"40543727","id":"PMC_40543727","title":"Reduced CD37 expression in B cell subsets after stimulation and its clinical relevance in primary Sjögren's syndrome.","date":"2025","source":"Immunology letters","url":"https://pubmed.ncbi.nlm.nih.gov/40543727","citation_count":0,"is_preprint":false},{"pmid":"42216090","id":"PMC_42216090","title":"A first-in-class bifunctional antibody targeting CD20 and CD37 remodels the immune microenvironment in relapsed or refractory B-cell malignancies.","date":"2026","source":"Journal of hematology & oncology","url":"https://pubmed.ncbi.nlm.nih.gov/42216090","citation_count":0,"is_preprint":false},{"pmid":"42013843","id":"PMC_42013843","title":"Debio 1562M CD37-targeting ADC is highly active and well tolerated in preclinical models of AML and MDS.","date":"2026","source":"Cell reports. Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/42013843","citation_count":0,"is_preprint":false},{"pmid":"41754790","id":"PMC_41754790","title":"A Phase II Study of 177Lu-Lilotomab Satetraxetan, a CD37 Antibody-Radionuclide Conjugate, as Third- or Later-Line Treatment of Rituximab-Refractory Follicular B-Cell Lymphoma Patients.","date":"2026","source":"Pharmaceuticals (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/41754790","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.02.24.639899","title":"DuoHexaBody-CD37 induces direct cytotoxic signaling in diffuse large B-cell lymphoma","date":"2025-02-28","source":"bioRxiv","url":"https://doi.org/10.1101/2025.02.24.639899","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":48998,"output_tokens":6955,"usd":0.12566,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":16231,"output_tokens":4529,"usd":0.09719,"stage2_stop_reason":"end_turn"},"total_usd":0.22285,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1988,\n      \"finding\": \"CD37 antigen (gp40-52) is a single-chain protein core of ~25 kDa with two N-linked complex carbohydrate chains comprising ~50% of total molecular mass; subcellular fractionation and electron microscopy showed it is associated with intracellular vesicles in addition to the cell surface, suggesting dual surface/cytoplasmic function.\",\n      \"method\": \"Biochemical analysis (immunoprecipitation, glycosidase treatment), electron microscopy, subcellular fractionation\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — direct biochemical characterization with EM localization, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"3257508\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1989,\n      \"finding\": \"CD37 is a 244-amino acid protein lacking a conventional leader sequence, with an N-terminal cytoplasmic domain followed by three transmembrane sequences within the first 110 amino acids and a hydrophilic C-terminal region containing three N-glycosylation sites, establishing its topology as a four-transmembrane protein.\",\n      \"method\": \"cDNA cloning and sequence analysis, comparison with rat OX-44 NH2-terminal protein sequence\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cDNA cloning with protein sequence validation, single lab, orthogonal protein and nucleotide approaches\",\n      \"pmids\": [\"2466944\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"CD37 gene is located on human chromosome 19 (region 19p13–q13.4), distinct from paralogous tetraspanins CD53 (chr 1) and R2/C33 (chr 11).\",\n      \"method\": \"Human/rodent somatic cell hybrid panel mapping with human-specific probes and deletion hybrid regional assignment\",\n      \"journal\": \"Immunogenetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — standard chromosomal mapping using somatic cell hybrids, single lab\",\n      \"pmids\": [\"8436422\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"CD37 co-precipitates with MHC class II (DR) glycoproteins as part of large multicomponent membrane complexes also containing CD53, TAPA-1, R2/C33, CD19, and CD21 in B cells, indicating CD37 resides in tetraspanin-enriched microdomains physically associated with MHC class II.\",\n      \"method\": \"Co-immunoprecipitation and preclearing experiments from mild detergent lysates of human B-cell lines and tonsillar B cells\",\n      \"journal\": \"Immunogenetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — reciprocal co-precipitation in multiple cell types, single lab, single method (co-IP)\",\n      \"pmids\": [\"8119731\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"CD37-deficient mice show selectively impaired T-cell-dependent IgG1 antibody responses (reduced serum IgG1, poor responses to antigen without adjuvant and to viral infections), demonstrating a role for CD37 in T cell–B cell interactions under suboptimal costimulatory conditions; lymphoid organ development was normal.\",\n      \"method\": \"Targeted gene inactivation (knockout mice), immunization experiments, serum immunoglobulin measurement, flow cytometry\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO model with defined humoral immune phenotype, multiple immunization conditions tested, replicated across immune challenges\",\n      \"pmids\": [\"10891477\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"CD37 negatively regulates T cell proliferation by modulating early TCR signaling: CD37-deficient T cells are hyperproliferative with enhanced IL-2 production and increased CD4/CD8-associated p56Lck kinase activity; cross-linking CD37 on human T cells inhibited CD3-induced proliferation.\",\n      \"method\": \"CD37 knockout mice, MLR, Con A and anti-CD3 stimulation assays, division cycle analysis, p56Lck kinase activity assay, CD37 cross-linking on human T cells\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO mouse phenotype replicated across multiple stimulation conditions, biochemical kinase activity measurement, and human T cell cross-linking functional assay\",\n      \"pmids\": [\"14978098\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Dectin-1 functionally interacts with tetraspanin CD37 on APC surfaces; CD37 stabilizes dectin-1 at the plasma membrane by preventing its internalization, and CD37 deficiency results in a 10-fold increase in dectin-1-induced IL-6 production in macrophages despite reduced surface dectin-1 levels.\",\n      \"method\": \"CD37-/- mice, confocal colocalization, dectin-1 internalization assay, transfection of CD37 into macrophage cell line, cytokine measurement after curdlan (specific dectin-1 ligand) stimulation\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO macrophages, CD37 transfection rescue, ligand-specific stimulation, multiple orthogonal methods in one study\",\n      \"pmids\": [\"17182550\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"CD37 inhibits IgA immune responses in vivo; CD37-deficient mice show 15-fold elevated serum IgA and increased IgA+ plasma cells in spleen, MALT, and bone marrow. This was directly attributable to CD37 deficiency on B cells (shown by bone marrow chimeras). Mechanistically, CD37 deficiency elevates germinal center IL-6, and neutralizing IL-6 in vivo reverses the increased IgA response.\",\n      \"method\": \"CD37-/- mice, bone marrow chimeric mice, in vivo IL-6 neutralization, immunization, serum Ig measurement, ELISPOT\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — bone marrow chimeras establish B cell-intrinsic mechanism, IL-6 neutralization rescue provides causal pathway placement, multiple orthogonal methods\",\n      \"pmids\": [\"19282981\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"CD37 and CD151 differentially regulate dendritic cell function: CD37-deficient DCs are hyper-stimulatory to T cells through enhanced peptide/MHC presentation, while CD151 controls co-stimulation, demonstrating that CD37 restrains antigen presentation by DCs.\",\n      \"method\": \"CD37-/- and CD151-/- mouse DC functional assays, peptide/MHC presentation to antigen-specific T cells, T cell activation readouts\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two parallel KO models tested, antigen-specific T cell readout, dissection of two distinct mechanisms in one study\",\n      \"pmids\": [\"19089816\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"CD37 directly mediates signal transduction upon ligation: it becomes tyrosine phosphorylated and associates with proximal signaling molecules. Two functionally opposing tyrosine residues were identified: a Y in the N-terminal 'ITIM-like' motif mediates SHP1-dependent apoptotic signaling, while a Y in the C-terminal 'ITAM motif' mediates PI3K-dependent survival signaling.\",\n      \"method\": \"CD37 ligation with bivalent SMIP molecule, phosphotyrosine immunoprecipitation, mutagenesis of ITIM/ITAM tyrosine residues, SHP1 and PI3K pathway assays, apoptosis assays\",\n      \"journal\": \"Cancer cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — active-site mutagenesis identifying specific tyrosine residues with opposing functions, biochemical pathway characterization, direct signaling assays\",\n      \"pmids\": [\"22624718\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"CD37 is required for α4β1 integrin-dependent Akt survival signaling in IgG-secreting plasma cells: CD37-deficient plasma cells show impaired α4β1 integrin mobility and clustering in the plasma membrane upon VCAM-1 binding, leading to defective downstream Akt activation, increased apoptosis in germinal centers, and reduced numbers of long-lived plasma cells.\",\n      \"method\": \"CD37-/- mice, flow cytometry of plasma cell populations, apoptosis assays, integrin mobility/clustering assays, Akt phosphorylation assays, bone marrow immunoglobulin secretion quantification\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO mouse model with defined cellular phenotype, mechanistic dissection of integrin clustering and Akt pathway, multiple orthogonal methods\",\n      \"pmids\": [\"23150881\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CD37 ablation impairs dendritic cell migration from skin to draining lymph nodes, chemotactic migration, integrin-mediated adhesion under flow, cell spreading and actin protrusion formation, and in vivo priming of naive T cells; multiphoton microscopy showed reduced migration rate and increased randomness of DC movement in CD37-/- mice.\",\n      \"method\": \"CD37-/- mice, in vivo DC migration assays (skin painting), multiphoton microscopy, flow chamber adhesion assay, chemotaxis assay, adoptive T cell transfer priming assay\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple in vivo and in vitro migration assays in KO mice, live imaging, multiple mechanistic readouts\",\n      \"pmids\": [\"23420539\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"CD37 directly interacts with SOCS3 (suppressor of cytokine signaling 3); CD37 deficiency drives constitutive activation of the IL-6 signaling pathway. CD37-/- mice develop germinal center-derived B cell lymphoma, and double Cd37/Il6 knockout mice are fully protected from lymphoma, placing CD37 upstream of IL-6 signaling as a tumor suppressor.\",\n      \"method\": \"CD37-/- mice, co-immunoprecipitation (CD37–SOCS3 interaction), double Cd37/Il6 knockout mice, IL-6 pathway activation assays, lymphoma incidence scoring\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis via double KO fully rescuing lymphoma phenotype, direct biochemical interaction identified by co-IP, causal pathway confirmed\",\n      \"pmids\": [\"26784544\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"CD37 and CD82 have opposing roles in DC biology via differential activation of small GTPases: CD37 promotes activation of Rac-1 to support cell spreading and migration, while CD82 negatively regulates RhoA; both tetraspanins negatively regulate Cdc42. CD37 ablation impairs actin protrusions and cell spreading on fibronectin.\",\n      \"method\": \"CD37-/- and CD82-/- BMDC functional assays, small GTPase activity assays (Rac-1, RhoA, Cdc42), cell spreading and migration assays, MHC class II maturation assays\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two parallel KO models, direct GTPase activity measurements, multiple orthogonal functional readouts\",\n      \"pmids\": [\"26729805\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CD37 regulates β2 integrin-mediated neutrophil adhesion and migration: CD37-/- neutrophils show impaired adhesion to ICAM-1 despite normal high-affinity β2 integrin display, impaired actin polymerization, reduced cell spreading and polarization, dysregulated Rac-1 activation, and accelerated β2 integrin internalization. Superresolution microscopy showed CD37 and CD18 do not significantly co-cluster, indicating CD37 acts downstream of integrin engagement on cytoskeletal function rather than via direct integrin interaction.\",\n      \"method\": \"CD37-/- mice, intravital microscopy, in vitro flow chamber adhesion assay, superresolution microscopy, Rac-1 activation assay, actin polymerization assay, integrin internalization assay\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO mouse in vivo and in vitro, superresolution imaging rules out direct molecular interaction, Rac-1 biochemical assay, multiple orthogonal methods\",\n      \"pmids\": [\"26566675\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CLEC-2-dependent DC migration is controlled by CD37: CD37 specifically interacts with CLEC-2; Cd37-/- DCs show reduced surface CLEC-2, impaired adhesion and migration on lymph node stromal cells, failure to form actin protrusions upon podoplanin-induced CLEC-2 stimulation, and failure to inhibit actomyosin contractility in stromal cells. CD37 is required for CLEC-2 recruitment to its ligand podoplanin in the membrane.\",\n      \"method\": \"Co-immunoprecipitation (CD37–CLEC-2 interaction), Cd37-/- DCs, microcontact printing, 3D collagen matrix migration assay, CLEC-2 internalization/surface expression measurement\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct biochemical interaction shown by co-IP, KO phenotyping, microcontact printing for membrane recruitment, multiple orthogonal assays\",\n      \"pmids\": [\"30185523\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"IL-6 is essential for glomerular IgA deposition and renal pathology in CD37-deficient mice: Cd37-/-/Il6-/- double-knockout mice show no glomerular IgA deposition and are protected from exacerbated renal failure, establishing that CD37 normally suppresses IgA nephropathy-like disease by inhibiting the IL-6 pathway.\",\n      \"method\": \"Cd37-/- mice, Cd37/Il6 double-knockout mice, anti-GBM nephritis induction, serum IL-6 measurement, immunofluorescence for IgA deposition, histopathology\",\n      \"journal\": \"Kidney international\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis via double KO fully rescuing pathology, LPS challenge model, multiple pathological readouts\",\n      \"pmids\": [\"29551516\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CD37 acts as an inhibitor of fatty acid (FA) metabolism in lymphoma by directly interacting with the FA transporter FATP1; deletion of CD37 increases FA oxidation and uptake of exogenous palmitate into energy and membrane building blocks, a phenotype reversed by FATP1 inhibition.\",\n      \"method\": \"CD37 knockout lymphoma cells, co-immunoprecipitation (CD37–FATP1 interaction), functional FA oxidation assays, metabolomics, serum palmitate depletion in mouse studies, FATP1 inhibitor rescue experiments, patient lymphoma tissue lipid staining\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct protein–protein interaction by co-IP, functional rescue by FATP1 inhibition, metabolomics, in vivo mouse data, patient tissue confirmation\",\n      \"pmids\": [\"36100608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"IRF8 is a transcriptional activator of CD37 expression in DLBCL: IRF8 directly binds the CD37 promoter (confirmed by DNA pulldown/MS and ChIP), IRF8 overexpression increases CD37 protein levels, and CRISPR/Cas9 knockout of IRF8 decreases CD37 levels in DLBCL cell lines. CD37-negative DLBCL specifically lacks CD37 promoter activity independent of promoter DNA methylation.\",\n      \"method\": \"Quantitative nuclear proteomics, DNA pulldown + mass spectrometry, targeted ChIP, CRISPR/Cas9 IRF8 knockout, IRF8 overexpression, promoter methylation analysis, IHC (n=206 primary DLBCL)\",\n      \"journal\": \"Blood advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — direct promoter binding by ChIP and DNA pulldown-MS, loss-of-function and gain-of-function in multiple cell lines, large patient cohort validation\",\n      \"pmids\": [\"35086136\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"N-glycosylation of CD37 is required for its surface expression: glycosylation mutants of CD37 show impaired cell surface localization. Glycosylation affects CD37 interaction with partner proteins CD53 and CD20 in a localization-dependent manner, but CD37 interaction with IL-6Rα is glycosylation-independent.\",\n      \"method\": \"Generation of CD37 glycosylation mutants, flow cytometry for surface expression, dSTORM single-molecule superresolution microscopy for nanoscale membrane organization, co-immunoprecipitation for partner protein interactions\",\n      \"journal\": \"Biophysical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — mutagenesis of glycosylation sites, superresolution imaging, co-IP for multiple partner interactions, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"38031400\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CD37 forms a complex with CD20, and CD20 stabilizes CD37 in the cell membrane; CD20 knockout cells show major downregulation of CD37, increased CD37 internalization rate, and reduced efficacy of anti-CD37 complement-dependent cytotoxicity that is partially restored by lysosome inhibition.\",\n      \"method\": \"CD20 knockout cell lines, co-immunoprecipitation (CD20–CD37 complex), flow cytometry for surface CD37, internalization assay, CDC assay, lysosome inhibitor rescue\",\n      \"journal\": \"Oncoimmunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct complex shown by co-IP, KO functional rescue, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"38846084\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CD37 interacts with integrin α4β7 in AML cells and activates the PI3K-AKT pathway mediated by integrin signaling; CD37 knockdown in AML retards proliferation and increases apoptosis, and CD37 deficiency in vivo impairs leukemia maintenance and LSC self-renewal (serial transplantation) without affecting normal hematopoiesis.\",\n      \"method\": \"Co-immunoprecipitation (CD37–integrin α4β7), CD37 knockdown in human AML cell lines, CD37-deficient mouse AML model, serial transplantation assay, PI3K-AKT phosphorylation assays, colony formation assay\",\n      \"journal\": \"Stem cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct protein interaction by co-IP, in vivo KO model, signaling pathway measurement, single lab\",\n      \"pmids\": [\"40250439\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CD37 acts as a phagocytic checkpoint in macrophages: tumorous macrophage migration inhibitory factor (MIF) directly binds CD37, promoting phosphorylation of CD37 Y13 and activating a signaling cascade involving SHP1 recruitment and AKT inhibition that impairs phagocytosis. Targeting CD37 with an antibody promotes phagocytosis of multiple cancer cell types in vitro and tumor clearance in vivo.\",\n      \"method\": \"In vitro phagocytosis assays, ribosome profiling of sorted macrophages, direct binding assay (MIF–CD37), CD37 Y13 phosphorylation measurement, SHP1 recruitment assay, AKT signaling assay, CD37 KO macrophages, in vivo preclinical mouse tumor models\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — direct protein–protein binding established, site-specific phosphorylation identified, downstream signaling cascade characterized, in vitro reconstitution + in vivo multiple tumor models\",\n      \"pmids\": [\"40675974\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CD37 is in close proximity to the BCR in B cells; CRISPR knockout of CD37 heightens BCR signaling, slows BCR endocytosis, and reduces peptide-MHC class II complex formation, demonstrating that CD37 modulates BCR function at the membrane.\",\n      \"method\": \"Proximity-based biotinylation (BioID) + mass spectrometry, CRISPR/Cas9 CD37 knockout in B cell line, BCR signaling assay, BCR endocytosis assay, peptide-MHC class II presentation assay\",\n      \"journal\": \"ImmunoHorizons\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proximity labeling identifies BCR association, CRISPR KO with three functional readouts, single lab\",\n      \"pmids\": [\"38625120\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CD37 positively regulates platelet activation and thrombosis: Cd37-/- platelets exhibit impaired integrin αIIbβ3 signaling (reduced fibrinogen spreading and agonist-induced αIIbβ3 activation); chimeric mice reconstituted with Cd37-/- bone marrow showed significantly increased time to vessel occlusion in the FeCl3 carotid artery thrombosis model, without effects on hemostasis.\",\n      \"method\": \"Cd37-/- mice, bone marrow chimera thrombosis model (FeCl3 carotid artery), platelet aggregation assays, integrin αIIbβ3 activation assay, fibrinogen spreading assay, coagulation metrics, RNA-sequencing of human and mouse platelets\",\n      \"journal\": \"Cardiovascular research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO mouse in vivo thrombosis model, bone marrow chimeras establish cell-autonomous platelet function, biochemical integrin signaling assays, human and mouse data\",\n      \"pmids\": [\"40126944\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"DuoHexaBody-CD37 induces direct cytotoxicity in DLBCL by inducing CD37 clustering at the cell surface (without internalization) and predominantly upregulating p-SHP1(Y564) in DLBCL cells. In primary B cells, the same antibody activates p-AKT(S473) and MAPK survival signaling. The N-terminus of CD37 is required for DuoHexaBody-CD37-induced signaling, established using CD37 N-terminal mutants.\",\n      \"method\": \"Unbiased phosphoproteomic screening (26 phosphoproteins), CD37 clustering imaging, CD37 N-terminal mutants, p-SHP1 and p-AKT signaling assays, cytotoxicity assays in DLBCL cell lines and primary B cells\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phosphoproteomics with site-specific readouts, N-terminal mutagenesis establishes domain requirement, preprint not yet peer-reviewed\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"CD37 is a four-transmembrane tetraspanin glycoprotein that functions as a direct signal transducer and membrane organizer in B cells, T cells, dendritic cells, neutrophils, and platelets: upon ligation it undergoes tyrosine phosphorylation at opposing ITIM-like (N-terminal, Y13/SHP1-dependent pro-apoptotic) and ITAM-like (C-terminal, PI3K-dependent pro-survival) motifs; it scaffolds α4β1 and α4β7 integrins in the plasma membrane to sustain Akt survival signaling; it stabilizes partner receptors (dectin-1, CLEC-2) at the cell surface and thereby controls downstream IL-6 production and DC migration via Rac-1 activation; it directly suppresses fatty acid uptake by inhibiting FATP1; it interacts with SOCS3 to restrain constitutive IL-6 signaling and lymphomagenesis; it modulates BCR endocytosis and antigen presentation; in macrophages it receives MIF-driven phosphorylation at Y13 to recruit SHP1 and inhibit AKT, acting as a phagocytic checkpoint; and its expression is transcriptionally activated by IRF8 and stabilized at the membrane by its complex partner CD20.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CD37 is a four-transmembrane tetraspanin glycoprotein that functions as a membrane organizer and bidirectional signal transducer in immune cells, platelets, and macrophages, controlling humoral immunity, cell migration, and survival signaling [#1, #9]. It resides within tetraspanin-enriched membrane microdomains physically associated with MHC class II and other tetraspanins and B-cell coreceptors [#3], and its N-glycosylation is required for surface delivery and for governing interactions with partner proteins including CD53 and CD20 [#19]. Upon ligation CD37 is tyrosine phosphorylated on two functionally opposing motifs: an N-terminal ITIM-like tyrosine that recruits SHP1 to drive apoptotic signaling and a C-terminal ITAM-like tyrosine that engages PI3K for survival signaling [#9, #25]. CD37 organizes and stabilizes partner receptors at the membrane—it prevents internalization of dectin-1 and recruits CLEC-2 to its ligand podoplanin—and these activities, together with Rac-1 activation and integrin-dependent adhesion, drive dendritic-cell spreading and migration [#6, #15, #13]. Through its restraint of IL-6 signaling, in part via direct interaction with SOCS3, CD37 suppresses IgA responses, IgA nephropathy-like renal pathology, and germinal-center-derived B-cell lymphoma, with double Cd37/Il6 knockout fully reversing lymphoma and renal disease [#12, #7, #16]. In malignancy CD37 also engages α4 integrins to sustain Akt survival signaling in plasma cells and AML, suppresses fatty-acid uptake by inhibiting FATP1, and acts as a macrophage phagocytic checkpoint when MIF binding triggers Y13 phosphorylation, SHP1 recruitment, and AKT inhibition [#10, #17, #21, #22]. CD37 expression is transcriptionally activated by IRF8 binding the CD37 promoter [#18], and its surface stability is reinforced by complex formation with CD20 [#20].\",\n  \"teleology\": [\n    {\n      \"year\": 1989,\n      \"claim\": \"Defining CD37's primary structure and membrane topology established it as a four-transmembrane tetraspanin, providing the structural framework for all later functional work.\",\n      \"evidence\": \"cDNA cloning and sequence analysis with rat OX-44 protein sequence comparison\",\n      \"pmids\": [\"2466944\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No high-resolution structure\", \"Functional role of individual domains not yet defined at this stage\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Showing CD37 co-precipitates with MHC class II and other tetraspanins and B-cell coreceptors placed it within tetraspanin-enriched membrane microdomains, framing it as a membrane organizer rather than a solitary receptor.\",\n      \"evidence\": \"Reciprocal co-immunoprecipitation from mild detergent lysates of human B cells\",\n      \"pmids\": [\"8119731\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry and direct versus indirect contacts within the complex unresolved\", \"Functional consequence of MHC II association not tested\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Knockout phenotyping revealed CD37 as a negative regulator of immune cell activation, showing impaired T-cell-dependent IgG1 responses yet hyperproliferative T cells with elevated p56Lck activity.\",\n      \"evidence\": \"CD37 knockout mice, immunization, MLR/anti-CD3 stimulation, p56Lck kinase assay, human T-cell cross-linking\",\n      \"pmids\": [\"10891477\", \"14978098\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link between CD37 and Lck regulation not defined\", \"Mechanism of selective IgG1 defect unexplained\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Parallel studies established CD37 as a restraint on antigen-presenting cell function and IgA responses, with bone marrow chimeras and IL-6 neutralization pinpointing a B-cell-intrinsic, IL-6-dependent mechanism.\",\n      \"evidence\": \"CD37-/- and CD151-/- DC presentation assays; bone marrow chimeras and in vivo IL-6 neutralization\",\n      \"pmids\": [\"19089816\", \"19282981\", \"17182550\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How CD37 loss elevates IL-6 not yet mechanistically explained at this stage\", \"Receptor partners mediating presentation restraint partly unknown\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identification of opposing N-terminal ITIM-like (SHP1/pro-apoptotic) and C-terminal ITAM-like (PI3K/pro-survival) tyrosine motifs established CD37 as a direct bidirectional signal transducer, and integrin/Akt work tied it to plasma-cell survival.\",\n      \"evidence\": \"SMIP ligation, phosphotyrosine IP, ITIM/ITAM tyrosine mutagenesis; KO plasma-cell integrin clustering and Akt assays\",\n      \"pmids\": [\"22624718\", \"23150881\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinases phosphorylating each motif not defined\", \"Switch determining ITIM versus ITAM engagement unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Linking CD37 to Rac-1 activation, actin protrusion, integrin adhesion and dendritic-cell migration defined its cytoskeletal-regulatory role in immune cell motility.\",\n      \"evidence\": \"CD37-/- DC in vivo migration, multiphoton imaging, flow adhesion, chemotaxis, and GTPase activity assays (CD37 vs CD82)\",\n      \"pmids\": [\"23420539\", \"26729805\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct effector linking CD37 to Rac-1 unknown\", \"Whether GTPase regulation is via partner receptors not resolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Discovery of CD37–SOCS3 interaction and Cd37/Il6 double-knockout rescue placed CD37 upstream of IL-6 signaling as a tumor suppressor whose loss drives germinal-center B-cell lymphoma.\",\n      \"evidence\": \"CD37-/- mice, CD37–SOCS3 co-IP, double Cd37/Il6 KO epistasis, lymphoma scoring\",\n      \"pmids\": [\"26784544\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Biochemical basis of SOCS3-mediated IL-6 restraint not fully resolved\", \"Contribution of cell-extrinsic IL-6 sources unclear\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"CD37 was shown to stabilize and recruit the partner receptor CLEC-2 to podoplanin to drive DC migration, and to suppress IL-6-dependent IgA nephropathy-like renal disease, generalizing its receptor-organizing and IL-6-restraining functions.\",\n      \"evidence\": \"CD37–CLEC-2 co-IP, microcontact printing, 3D migration; Cd37/Il6 double KO anti-GBM nephritis model\",\n      \"pmids\": [\"30185523\", \"29551516\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of CLEC-2 recruitment unknown\", \"How CD37 simultaneously stabilizes diverse partner receptors not unified\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"CD37 was identified as a direct inhibitor of fatty-acid metabolism via FATP1 and as a transcriptional target of IRF8, connecting membrane CD37 to lymphoma metabolism and to the upstream control of its own expression.\",\n      \"evidence\": \"CD37–FATP1 co-IP, FA oxidation/metabolomics, FATP1 inhibitor rescue; IRF8 ChIP/DNA pulldown-MS, IRF8 KO/overexpression, DLBCL cohort\",\n      \"pmids\": [\"36100608\", \"35086136\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which CD37 inhibits FATP1 transport activity not defined\", \"Other transcriptional regulators of CD37 not surveyed\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Multiple studies extended CD37's role to integrin-driven AKT survival in AML, BCR modulation in B cells, CD20-dependent membrane stabilization, and a MIF-triggered Y13/SHP1 phagocytic checkpoint in macrophages, unifying it as a membrane scaffold controlling survival and effector signaling.\",\n      \"evidence\": \"CD37–α4β7 co-IP and AML KO model; BioID BCR proximity and CRISPR KO; CD20 KO complex/internalization assays; MIF–CD37 binding, Y13 phosphorylation, SHP1/AKT and phagocytosis assays\",\n      \"pmids\": [\"40250439\", \"38625120\", \"38846084\", \"40675974\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether α4β7 and α4β1 use shared signaling machinery unresolved\", \"Direct MIF–CD37 binding interface not structurally defined\", \"CD20 dependence of CD37 stability across cell types not generalized\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Platelet studies revealed CD37 as a positive regulator of αIIbβ3 integrin signaling and thrombosis, broadening its integrin-organizing function beyond immune cells, while antibody-clustering studies refined the N-terminal requirement for SHP1-biased signaling.\",\n      \"evidence\": \"Cd37-/- platelet aggregation, αIIbβ3 activation and FeCl3 thrombosis chimeras; DuoHexaBody-CD37 clustering, phosphoproteomics and N-terminal mutants (preprint)\",\n      \"pmids\": [\"40126944\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism coupling CD37 to platelet integrin inside-out/outside-in signaling unknown\", \"Cell-type basis for opposing positive vs negative integrin effects unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How CD37 mechanistically switches between its opposing ITIM/SHP1 and ITAM/PI3K outputs and coordinates its many partner receptors across distinct cell types remains the central unresolved question.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of CD37 in complex with any partner\", \"Kinases and adaptors selecting ITIM versus ITAM signaling unidentified\", \"Determinants of context-dependent positive versus negative integrin regulation unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [9, 22, 25]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [6, 12, 15, 17, 20]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [9, 10, 21]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [3, 19]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1, 3, 19]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [4, 5, 7, 8, 23]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [9, 10, 21, 22]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [12, 16, 17, 22]},\n      {\"term_id\": \"R-HSA-109582\", \"supporting_discovery_ids\": [24]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [17]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [18]}\n    ],\n    \"complexes\": [\n      \"tetraspanin-enriched microdomain (with MHC class II, CD53, TAPA-1, CD19, CD21)\",\n      \"CD37–CD20 complex\"\n    ],\n    \"partners\": [\n      \"SOCS3\",\n      \"CLEC-2\",\n      \"FATP1\",\n      \"CD20\",\n      \"CD53\",\n      \"ITGA4\",\n      \"MIF\",\n      \"IL6R\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}