{"gene":"BTN2A1","run_date":"2026-06-09T22:02:45","timeline":{"discoveries":[{"year":2021,"finding":"BTN2A1 is required for BTN3A-mediated Vγ9Vδ2 T cell cytotoxicity against cancer cells; co-expression of BTN2A1 and BTN3A1 is sufficient to trigger Vγ9Vδ2 TCR activation. BTN2A1 interacts with all three BTN3A isoforms (BTN3A1, BTN3A2, BTN3A3), and BTN3A interaction is rate-limiting for BTN2A1 export to the plasma membrane. BTN2A1/BTN3A1 interaction is enhanced by phosphoantigens (pAgs), and B30.2 domains of both proteins are required for pAg responsiveness. Anti-BTN2A1 monoclonal antibodies inhibit Vγ9Vδ2 T cell killing by blocking BTN2A1 binding to the Vγ9Vδ2 TCR.","method":"Cancer cell cytotoxicity assays, monoclonal antibody inhibition, co-expression experiments, flow cytometry","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (functional cytotoxicity assay, antibody inhibition, co-expression reconstitution, domain mutagenesis) in a single focused study","pmids":["34260935"],"is_preprint":false},{"year":2007,"finding":"BTN2A1 is a cell surface glycoprotein and novel ligand for DC-SIGN on immature monocyte-derived dendritic cells. Binding requires Ca2+, is mediated by high-mannose oligosaccharides on BTN2A1, and is dependent on IL-4-induced DC-SIGN expression during early dendritic cell differentiation. Tumor cell BTN2A1 (e.g., HEK293T) carries more high-mannose moieties than normal cells (e.g., HUVECs), governing differential recognition by DC-SIGN.","method":"Ig-fusion protein binding assays, DC-SIGN-transfectant binding, anti-DC-SIGN antibody inhibition, glycosylation analysis","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal binding assays (fusion protein, transfectant, antibody inhibition, glycosylation characterization) in a single study","pmids":["17785817"],"is_preprint":false},{"year":2023,"finding":"NMR and mutagenesis established that BTN2A1-IgV interacts with BTN3A1-IgV in a cis cell-surface structural model, but TCR and BTN3A1-IgV binding to BTN2A1-IgV are mutually exclusive due to binding site overlap. The BTN2A1-IgV/BTN3A1-IgV interaction is non-essential for recognition. A molecular surface on BTN3A1-IgV distinct from the BTN2A1 interface is essential for pAg sensing, supporting a composite-ligand model where germline TCR/BTN2A1 and clonotypic TCR/BTN3A interactions cooperate.","method":"NMR, structural modeling, site-directed mutagenesis, functional TCR activation assays","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR structure determination combined with mutagenesis and functional TCR activation assays in a single rigorous study","pmids":["36995939"],"is_preprint":false},{"year":2023,"finding":"BTN2A1 B30.2 domain forms a homodimer; single point mutations L318G and L325G in the linker region near the B30.2 domain block phosphoantigen response. L325G but not L318G prevents homodimerization of BTN2A1 internal domain constructs and abolishes binding to HMBPP-bound BTN3A1 (measured by ITC). HMBPP binds to BTN3A1 but not BTN2A1 (confirmed by [31P]-NMR). Disulfide-linked homodimerization via C247/C265 is not required for T cell IFN-γ stimulation.","method":"Site-directed mutagenesis, size exclusion chromatography, NMR (including [31P]-NMR and standard NMR), isothermal titration calorimetry (ITC), T cell IFN-γ ELISA","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with mutagenesis, ITC binding assays, and NMR, multiple orthogonal methods in one study","pmids":["37171180"],"is_preprint":false},{"year":2024,"finding":"BTN2A1 engagement by an agonist anti-BTN2A1 monoclonal antibody (107G3B5) enhances Vγ9Vδ2 T cell cytotoxicity against hematologic and solid tumor cell lines, and activates caspase 3/7 in tumor cells, triggering tumor cell death by pyroptosis.","method":"Cytotoxicity assays, holotomographic microscopy, caspase 3/7 activation assay, monoclonal antibody treatment","journal":"Cancer immunology research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional assays (cytotoxicity, caspase activation, live imaging) in a single study but no structural or biochemical reconstitution of the mechanism","pmids":["39302336"],"is_preprint":false},{"year":2024,"finding":"Anti-BTN2A1 monoclonal antibody engagement on M2-like macrophages induces SYK recruitment and sequential SYK and ERK (MAPK) phosphorylation, reprogramming M2-like macrophages toward an M1-like phenotype. Inhibition of SYK or ERK phosphorylation abolished this M2-to-M1 reprogramming.","method":"Monoclonal antibody treatment, kinase phosphorylation assays, SYK/ERK inhibitor experiments, ex vivo macrophage differentiation assays","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined signaling pathway by pharmacological inhibition of SYK and ERK with specific phenotypic readout, single lab, multiple methods","pmids":["39325623"],"is_preprint":false},{"year":2022,"finding":"A BTN2A1/BTN3A1 heterodimeric fusion protein provides 'signal 1' to activate Vγ9Vδ2+ T cells, but only in the presence of costimulatory signal via CD28 or NKG2D. A bispecific γδ T cell engager BTN2A1/3A1-Fc-CD19scFv alone enhanced granzyme B-mediated killing of CD19+ lymphoma cells when tumor cell costimulatory ligands satisfy 'signal 2'.","method":"Tumor cell-free T cell activation assay, cytotoxicity/granzyme B assay, heterodimeric fusion protein reconstitution","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional reconstitution with heterodimeric protein plus costimulatory dissection assays, single lab","pmids":["36096643"],"is_preprint":false},{"year":2025,"finding":"19F solution NMR of BTN3A1 point mutants revealed that residues W421, T449, and T506 in the B30.2 domain undergo conformational/dynamic changes upon HMBPP and BTN2A1 association, while juxtamembrane residues T304 and G323 are not affected. W421 is located at the BTN2A1 binding interface (its mutation reduces BTN2A1 binding affinity), and T506 perturbation indicates a larger conformational change of the BTN3A1 B30.2 domain upon binding both HMBPP and BTN2A1.","method":"19F solution NMR, site-directed mutagenesis of BTN3A1, binding affinity measurements","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — rigorous NMR method but single lab, single study, no independent replication","pmids":["40079188"],"is_preprint":false},{"year":2025,"finding":"BTN2A1 expression on lymphocytes increases via trogocytosis in the presence of activated myeloid cells (monocytes). BTN2A1-knockout B cells can acquire BTN2A1 from monocytes through trogocytosis, and BTN2A1-acquired normal or tumor cells exhibit higher sensitivity to Vγ9Vδ2 T cell lysis.","method":"BTN2A1 knockout cell lines, trogocytosis assay, cytotoxicity assay, flow cytometry","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — BTN2A1-KO reconstitution via trogocytosis with direct cytotoxicity readout, multiple methods, single lab","pmids":["41066236"],"is_preprint":false},{"year":2024,"finding":"Cryo-EM structures revealed that HMBPP (pAg) bridges the intracellular B30.2 domains of BTN3A1 and BTN2A1 in a full-length BTN3A1-BTN3A2-BTN2A1 complex. Upon TCR engagement, the BTN3A2-BTN2A1 ectodomain interaction dissociates, allowing BTN2A1 to bind the lateral surface of the Vγ9 chain while BTN3A2 binds the apical surface of the Vδ2 chain, supporting a 'pliers-like gripping' mechanism for TCR activation.","method":"Cryo-EM structural determination of full-length BTN complexes with and without TCR","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — cryo-EM structures (Tier 1 method) but preprint, not yet peer-reviewed, single study","pmids":["bio_10.1101_2024.10.02.616253"],"is_preprint":true},{"year":2024,"finding":"Single oncogenic mutations introduced into healthy colorectal or breast organoids are sufficient to upregulate surface-expressed BTN2A1 and enable Vγ9Vδ2 TCR binding to tumor cells. Full T cell activation additionally requires phosphorylation of juxtamembrane amino acids of BTN3A1, leading to activating heterodimerization of BTN2A1 and BTN3A1. Protein interactome mapping identified PHLDB2, SYNJ2, and CARMIL1 as key regulators of BTN2A1 and BTN3A1 surface dynamics during early malignant transformation.","method":"Genetically engineered step-wise mutagenesis organoid models, surface expression assays, Vγ9Vδ2 TCR binding assays, protein interactome mapping","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 2 / Weak — preprint, single study, novel interactors identified by interactome mapping without deep mechanistic validation of individual interactions","pmids":["bio_10.1101_2024.11.19.624272"],"is_preprint":true},{"year":2025,"finding":"The agonist antibody ICT01 (targeting BTN3As) destabilizes the BTN2A1-BTN3A interface and facilitates Vγ9Vδ2 TCR engagement, activating Vγ9Vδ2 T cells independently of phosphoantigens.","method":"Structural analysis, biochemical binding assays, cellular activation assays","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 2 / Weak — preprint, mechanistic claim about BTN2A1-BTN3A interface disruption supported by structural and biochemical data but not yet peer-reviewed","pmids":["bio_10.1101_2025.10.21.681109"],"is_preprint":true},{"year":2026,"finding":"Metformin upregulates BTN3A1 and BTN2A1 expression on esophageal cancer cells in an AMPK-dependent manner, sensitizing them to Vγ9Vδ2 T cell-mediated cytotoxicity and granzyme B-mediated apoptosis.","method":"AMPK inhibitor experiments, surface expression assays, cytotoxicity assays, xenograft models","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — AMPK-dependence established by pharmacological inhibition with functional cytotoxicity readout, in vitro and in vivo xenograft confirmation, single lab","pmids":["42248853"],"is_preprint":false}],"current_model":"BTN2A1 is a cell-surface butyrophilin that functions as a direct ligand for the Vγ9 chain of the Vγ9Vδ2 TCR, forming a pAg-enhanced heterodimeric complex with BTN3A1 (and other BTN3A isoforms) at the cell surface—where intracellular HMBPP bridges the cytoplasmic B30.2 domains of BTN3A1 and BTN2A1, inducing conformational changes that allow BTN2A1 to engage the TCR and trigger γδ T cell cytotoxicity—while also acting as a DC-SIGN ligand through tumor-associated high-mannose glycosylation, and signaling through SYK/ERK in macrophages to regulate their polarization state."},"narrative":{"mechanistic_narrative":"BTN2A1 is a cell-surface butyrophilin that serves as a direct, germline-encoded ligand for the Vγ9 chain of the Vγ9Vδ2 T cell receptor, functioning as the obligatory partner of BTN3A in phosphoantigen (pAg)-driven γδ T cell cytotoxicity against tumor cells [PMID:34260935]. Co-expression of BTN2A1 with BTN3A1 is sufficient to trigger Vγ9Vδ2 TCR activation; BTN2A1 interacts with all three BTN3A isoforms, and this interaction is rate-limiting for BTN2A1 export to the plasma membrane [PMID:34260935]. Phosphoantigen sensing operates through the intracellular B30.2 domains: HMBPP binds the B30.2 domain of BTN3A1, not BTN2A1, and bridges the two cytoplasmic domains, with BTN2A1 B30.2 homodimerization required for engagement of HMBPP-bound BTN3A1 [PMID:37171180, PMID:bio_10.1101_2024.10.02.616253]. At the cell surface the BTN2A1 and BTN3A IgV domains assemble in cis, but TCR and BTN3A1-IgV binding to BTN2A1-IgV are mutually exclusive, and pAg-induced conformational changes in the BTN3A1 B30.2 domain drive a rearrangement in which the BTN3A2–BTN2A1 ectodomain contact dissociates so that BTN2A1 engages the lateral surface of Vγ9 in a composite-ligand, 'pliers-like gripping' mechanism [PMID:36995939, PMID:40079188, PMID:bio_10.1101_2024.10.02.616253]. Tumor-specific upregulation of surface BTN2A1 follows oncogenic transformation and can be induced pharmacologically through AMPK signaling, and agonist anti-BTN2A1 antibodies enhance γδ T cell killing and trigger caspase 3/7-mediated tumor pyroptosis [PMID:39302336, PMID:42248853]. Independently of γδ T cell recognition, BTN2A1 is a Ca2+-dependent ligand for DC-SIGN on immature dendritic cells via high-mannose glycans enriched on tumor cells, and antibody engagement of BTN2A1 on M2-like macrophages drives SYK- and ERK-dependent reprogramming toward an M1-like phenotype [PMID:17785817, PMID:39325623].","teleology":[{"year":2007,"claim":"Before any γδ T cell role was known, BTN2A1 was first identified as a cell-surface glycoprotein ligand, establishing it as a glycan-dependent immune recognition molecule.","evidence":"Ig-fusion protein and DC-SIGN-transfectant binding assays with glycosylation analysis on dendritic cells","pmids":["17785817"],"confidence":"High","gaps":["Did not connect BTN2A1 to T cell biology or BTN3A","Functional consequence of DC-SIGN engagement for DC differentiation not resolved"]},{"year":2021,"claim":"Resolved the central question of what licenses BTN3A-mediated γδ T cell activation by identifying BTN2A1 as the required partner and a direct Vγ9Vδ2 TCR ligand.","evidence":"Cytotoxicity assays, co-expression reconstitution, antibody inhibition, and B30.2 domain mutagenesis in cancer cells","pmids":["34260935"],"confidence":"High","gaps":["Molecular geometry of the BTN2A1/BTN3A/TCR assembly unresolved","How pAg enhances the interaction not mechanistically defined"]},{"year":2022,"claim":"Established that BTN2A1/BTN3A1 provides 'signal 1' but requires costimulation, refining the requirements for productive γδ T cell engagement and enabling therapeutic engager design.","evidence":"Tumor cell-free activation assays with a BTN2A1/BTN3A1 heterodimeric fusion protein and CD28/NKG2D costimulation dissection","pmids":["36096643"],"confidence":"Medium","gaps":["Stoichiometry of the engineered heterodimer vs native complex unclear","Costimulatory ligand requirements in primary tumors not mapped"]},{"year":2023,"claim":"Defined the structural logic at the cell surface, showing TCR and BTN3A1-IgV binding to BTN2A1-IgV are mutually exclusive and supporting a composite-ligand model.","evidence":"NMR, structural modeling, mutagenesis, and TCR activation assays on IgV domains","pmids":["36995939"],"confidence":"High","gaps":["Cis IgV interaction shown non-essential, leaving its biological purpose open","Did not resolve the intracellular pAg-sensing step"]},{"year":2023,"claim":"Localized pAg sensing to the intracellular domains, demonstrating HMBPP binds BTN3A1 (not BTN2A1) and that BTN2A1 B30.2 homodimerization is required to engage HMBPP-bound BTN3A1.","evidence":"Mutagenesis, size-exclusion chromatography, [31P]-NMR, ITC, and IFN-γ ELISA on internal-domain constructs","pmids":["37171180"],"confidence":"High","gaps":["How intracellular B30.2 engagement is transmitted to ectodomain rearrangement not shown","Role of linker residues L318/L325 in full-length signaling untested"]},{"year":2024,"claim":"Demonstrated BTN2A1 is a druggable target by showing agonist antibody engagement enhances γδ T cell killing and triggers tumor pyroptosis.","evidence":"Cytotoxicity, caspase 3/7, and holotomographic imaging assays with antibody 107G3B5 on tumor lines","pmids":["39302336"],"confidence":"Medium","gaps":["Molecular basis of agonism not biochemically reconstituted","Pyroptotic pathway downstream of caspase activation not detailed"]},{"year":2024,"claim":"Extended BTN2A1 function beyond γδ T cells, showing antibody engagement reprograms M2-like macrophages toward M1 via a defined SYK/ERK signaling cascade.","evidence":"Antibody treatment with SYK/ERK inhibitor experiments and ex vivo macrophage differentiation assays","pmids":["39325623"],"confidence":"Medium","gaps":["Whether native ligands drive this signaling, or only the antibody, is unknown","Receptor proximal events linking BTN2A1 to SYK recruitment not defined"]},{"year":2024,"claim":"Provided a full-length structural mechanism showing pAg bridges the intracellular B30.2 domains and TCR engagement drives ectodomain rearrangement into a 'pliers-like' grip.","evidence":"Cryo-EM of full-length BTN3A1-BTN3A2-BTN2A1 complexes with and without TCR (preprint)","pmids":["bio_10.1101_2024.10.02.616253"],"confidence":"Medium","gaps":["Preprint, not peer-reviewed","Dynamics of the transition state between cis and TCR-bound states not captured"]},{"year":2024,"claim":"Linked BTN2A1 surface upregulation to oncogenic transformation and identified candidate regulators of its surface dynamics.","evidence":"Step-wise oncogenic mutagenesis in organoids with surface and interactome mapping (preprint)","pmids":["bio_10.1101_2024.11.19.624272"],"confidence":"Low","gaps":["Preprint; PHLDB2/SYNJ2/CARMIL1 interactions identified by interactome mapping without mechanistic validation","Causal link between specific oncogenic mutations and BTN2A1 induction not dissected"]},{"year":2025,"claim":"Resolved which BTN3A1 B30.2 residues undergo pAg- and BTN2A1-induced conformational change, mapping the dynamic basis of binding.","evidence":"19F solution NMR of BTN3A1 point mutants with binding affinity measurements","pmids":["40079188"],"confidence":"Medium","gaps":["Single lab, no independent replication","Conformational changes in BTN2A1 itself not similarly mapped"]},{"year":2025,"claim":"Showed BTN2A1 can be transferred between cells by trogocytosis, sensitizing recipient cells to γδ T cell lysis and expanding how BTN2A1 surface levels are regulated.","evidence":"BTN2A1-knockout cells, trogocytosis and cytotoxicity assays, flow cytometry","pmids":["41066236"],"confidence":"Medium","gaps":["In vivo relevance of trogocytic transfer unproven","Whether transferred BTN2A1 retains intracellular pAg-sensing capacity unaddressed"]},{"year":2026,"claim":"Demonstrated a pharmacological route to enhance γδ T cell sensitivity by showing metformin upregulates BTN2A1/BTN3A1 via AMPK.","evidence":"AMPK inhibitor experiments, surface expression and cytotoxicity assays, xenograft models in esophageal cancer","pmids":["42248853"],"confidence":"Medium","gaps":["Mechanism linking AMPK to BTN transcription/surface trafficking not defined","Effect generality across tumor types not established"]},{"year":null,"claim":"How the intracellular pAg-induced B30.2 engagement is mechanically transmitted across the membrane to drive the ectodomain rearrangement that licenses BTN2A1–Vγ9 binding remains incompletely defined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No peer-reviewed full-length structure capturing the transition","Surface trafficking regulators of BTN2A1 not mechanistically validated","Physiological (non-antibody) triggers of BTN2A1 signaling in macrophages unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[0,2,9]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,9]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1,9]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,1,5]}],"complexes":["BTN2A1-BTN3A1-BTN3A2 phosphoantigen-sensing complex"],"partners":["BTN3A1","BTN3A2","BTN3A3","DC-SIGN","TRGV9"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q7KYR7","full_name":"Butyrophilin subfamily 2 member A1","aliases":[],"length_aa":527,"mass_kda":59.6,"function":"","subcellular_location":"Membrane","url":"https://www.uniprot.org/uniprotkb/Q7KYR7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/BTN2A1","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CANX","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/BTN2A1","total_profiled":1310},"omim":[{"mim_id":"613595","title":"BUTYROPHILIN, SUBFAMILY 3, MEMBER A3; BTN3A3","url":"https://www.omim.org/entry/613595"},{"mim_id":"613594","title":"BUTYROPHILIN, SUBFAMILY 3, MEMBER A2; BTN3A2","url":"https://www.omim.org/entry/613594"},{"mim_id":"613593","title":"BUTYROPHILIN, SUBFAMILY 3, MEMBER A1; BTN3A1","url":"https://www.omim.org/entry/613593"},{"mim_id":"613590","title":"BUTYROPHILIN, SUBFAMILY 2, MEMBER A1; BTN2A1","url":"https://www.omim.org/entry/613590"},{"mim_id":"601610","title":"BUTYROPHILIN, SUBFAMILY 1, MEMBER A1; BTN1A1","url":"https://www.omim.org/entry/601610"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/BTN2A1"},"hgnc":{"alias_symbol":["BT2.1","BTF1","BTN2.1"],"prev_symbol":[]},"alphafold":{"accession":"Q7KYR7","domains":[{"cath_id":"2.60.40.10","chopping":"32-144","consensus_level":"high","plddt":95.4712,"start":32,"end":144},{"cath_id":"2.60.40.10","chopping":"151-240","consensus_level":"high","plddt":89.4316,"start":151,"end":240},{"cath_id":"2.60.120.920","chopping":"333-501","consensus_level":"high","plddt":89.464,"start":333,"end":501},{"cath_id":"1.20.5","chopping":"255-320","consensus_level":"medium","plddt":82.4177,"start":255,"end":320}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q7KYR7","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q7KYR7-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q7KYR7-F1-predicted_aligned_error_v6.png","plddt_mean":84.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=BTN2A1","jax_strain_url":"https://www.jax.org/strain/search?query=BTN2A1"},"sequence":{"accession":"Q7KYR7","fasta_url":"https://rest.uniprot.org/uniprotkb/Q7KYR7.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q7KYR7/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q7KYR7"}},"corpus_meta":[{"pmid":"34260935","id":"PMC_34260935","title":"BTN2A1, an immune checkpoint targeting Vγ9Vδ2 T cell cytotoxicity against malignant cells.","date":"2021","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/34260935","citation_count":77,"is_preprint":false},{"pmid":"17785817","id":"PMC_17785817","title":"The B7 homolog butyrophilin BTN2A1 is a novel ligand for DC-SIGN.","date":"2007","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/17785817","citation_count":47,"is_preprint":false},{"pmid":"21211798","id":"PMC_21211798","title":"Association of a polymorphism of BTN2A1 with myocardial infarction in East Asian populations.","date":"2010","source":"Atherosclerosis","url":"https://pubmed.ncbi.nlm.nih.gov/21211798","citation_count":44,"is_preprint":false},{"pmid":"36995939","id":"PMC_36995939","title":"Phosphoantigen sensing combines TCR-dependent recognition of the BTN3A IgV domain and germline interaction with BTN2A1.","date":"2023","source":"Cell 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hypertension","url":"https://pubmed.ncbi.nlm.nih.gov/21525964","citation_count":10,"is_preprint":false},{"pmid":"21468600","id":"PMC_21468600","title":"Association of polymorphisms of BTN2A1 and ILF3 with myocardial infarction in Japanese individuals with different lipid profiles.","date":"2011","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/21468600","citation_count":10,"is_preprint":false},{"pmid":"22977569","id":"PMC_22977569","title":"Association of a polymorphism of BTN2A1 with dyslipidemia in East Asian populations.","date":"2011","source":"Experimental and therapeutic medicine","url":"https://pubmed.ncbi.nlm.nih.gov/22977569","citation_count":10,"is_preprint":false},{"pmid":"39325623","id":"PMC_39325623","title":"BTN2A1 targeting reprograms M2-like macrophages and TAMs via SYK and MAPK signaling.","date":"2024","source":"Cell 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delta T/NK cell product GADEKILL as a novel immunotherapeutic tool for neuroblastoma patients: role of B7H6 and BTN2A1 in tumor cell killing.","date":"2026","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/41694338","citation_count":0,"is_preprint":false},{"pmid":"42248853","id":"PMC_42248853","title":"Metformin sensitizes esophageal squamous cell carcinoma to Vγ9Vδ2 T cell-mediated cytotoxicity by upregulating BTN3A1 and BTN2A1.","date":"2026","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/42248853","citation_count":0,"is_preprint":false},{"pmid":"40079188","id":"PMC_40079188","title":"Investigation of structural and dynamic properties of the Butyrophilin BTN3A1/BTN2A1 cytoplasmic complex by 19F solution NMR.","date":"2025","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/40079188","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.10.21.681109","title":"Molecular Mechanisms Underlying Human Vγ9Vδ2 T Cell Activation by Butyrophilin-3 (BTN3) Targeted Antibodies","date":"2025-10-21","source":"bioRxiv","url":"https://doi.org/10.1101/2025.10.21.681109","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.10.02.616253","title":"Cryo-EM structural insights into Vγ9Vδ2 TCR activation via multiple butyrophilins","date":"2024-10-03","source":"bioRxiv","url":"https://doi.org/10.1101/2024.10.02.616253","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.07.06.24309341","title":"Identification of Causal Risk Factors for Pan-Cancers: a Mendelian Randomization Study","date":"2024-07-07","source":"bioRxiv","url":"https://doi.org/10.1101/2024.07.06.24309341","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.11.19.624272","title":"Sensitivity to Vγ9Vδ2TCR T cells is imprinted after single mutations during early oncogenesis","date":"2024-11-21","source":"bioRxiv","url":"https://doi.org/10.1101/2024.11.19.624272","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":18114,"output_tokens":3833,"usd":0.055919,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":11404,"output_tokens":4041,"usd":0.079022,"stage2_stop_reason":"end_turn"},"total_usd":0.134941,"stage1_batch_id":"msgbatch_0179Z2pxRYBsXi2xADneafRw","stage2_batch_id":"msgbatch_01LaY9ZaVdgjWArcZo9eqQE5","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2021,\n      \"finding\": \"BTN2A1 is required for BTN3A-mediated Vγ9Vδ2 T cell cytotoxicity against cancer cells; co-expression of BTN2A1 and BTN3A1 is sufficient to trigger Vγ9Vδ2 TCR activation. BTN2A1 interacts with all three BTN3A isoforms (BTN3A1, BTN3A2, BTN3A3), and BTN3A interaction is rate-limiting for BTN2A1 export to the plasma membrane. BTN2A1/BTN3A1 interaction is enhanced by phosphoantigens (pAgs), and B30.2 domains of both proteins are required for pAg responsiveness. Anti-BTN2A1 monoclonal antibodies inhibit Vγ9Vδ2 T cell killing by blocking BTN2A1 binding to the Vγ9Vδ2 TCR.\",\n      \"method\": \"Cancer cell cytotoxicity assays, monoclonal antibody inhibition, co-expression experiments, flow cytometry\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (functional cytotoxicity assay, antibody inhibition, co-expression reconstitution, domain mutagenesis) in a single focused study\",\n      \"pmids\": [\"34260935\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"BTN2A1 is a cell surface glycoprotein and novel ligand for DC-SIGN on immature monocyte-derived dendritic cells. Binding requires Ca2+, is mediated by high-mannose oligosaccharides on BTN2A1, and is dependent on IL-4-induced DC-SIGN expression during early dendritic cell differentiation. Tumor cell BTN2A1 (e.g., HEK293T) carries more high-mannose moieties than normal cells (e.g., HUVECs), governing differential recognition by DC-SIGN.\",\n      \"method\": \"Ig-fusion protein binding assays, DC-SIGN-transfectant binding, anti-DC-SIGN antibody inhibition, glycosylation analysis\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal binding assays (fusion protein, transfectant, antibody inhibition, glycosylation characterization) in a single study\",\n      \"pmids\": [\"17785817\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NMR and mutagenesis established that BTN2A1-IgV interacts with BTN3A1-IgV in a cis cell-surface structural model, but TCR and BTN3A1-IgV binding to BTN2A1-IgV are mutually exclusive due to binding site overlap. The BTN2A1-IgV/BTN3A1-IgV interaction is non-essential for recognition. A molecular surface on BTN3A1-IgV distinct from the BTN2A1 interface is essential for pAg sensing, supporting a composite-ligand model where germline TCR/BTN2A1 and clonotypic TCR/BTN3A interactions cooperate.\",\n      \"method\": \"NMR, structural modeling, site-directed mutagenesis, functional TCR activation assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structure determination combined with mutagenesis and functional TCR activation assays in a single rigorous study\",\n      \"pmids\": [\"36995939\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"BTN2A1 B30.2 domain forms a homodimer; single point mutations L318G and L325G in the linker region near the B30.2 domain block phosphoantigen response. L325G but not L318G prevents homodimerization of BTN2A1 internal domain constructs and abolishes binding to HMBPP-bound BTN3A1 (measured by ITC). HMBPP binds to BTN3A1 but not BTN2A1 (confirmed by [31P]-NMR). Disulfide-linked homodimerization via C247/C265 is not required for T cell IFN-γ stimulation.\",\n      \"method\": \"Site-directed mutagenesis, size exclusion chromatography, NMR (including [31P]-NMR and standard NMR), isothermal titration calorimetry (ITC), T cell IFN-γ ELISA\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with mutagenesis, ITC binding assays, and NMR, multiple orthogonal methods in one study\",\n      \"pmids\": [\"37171180\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"BTN2A1 engagement by an agonist anti-BTN2A1 monoclonal antibody (107G3B5) enhances Vγ9Vδ2 T cell cytotoxicity against hematologic and solid tumor cell lines, and activates caspase 3/7 in tumor cells, triggering tumor cell death by pyroptosis.\",\n      \"method\": \"Cytotoxicity assays, holotomographic microscopy, caspase 3/7 activation assay, monoclonal antibody treatment\",\n      \"journal\": \"Cancer immunology research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional assays (cytotoxicity, caspase activation, live imaging) in a single study but no structural or biochemical reconstitution of the mechanism\",\n      \"pmids\": [\"39302336\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Anti-BTN2A1 monoclonal antibody engagement on M2-like macrophages induces SYK recruitment and sequential SYK and ERK (MAPK) phosphorylation, reprogramming M2-like macrophages toward an M1-like phenotype. Inhibition of SYK or ERK phosphorylation abolished this M2-to-M1 reprogramming.\",\n      \"method\": \"Monoclonal antibody treatment, kinase phosphorylation assays, SYK/ERK inhibitor experiments, ex vivo macrophage differentiation assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined signaling pathway by pharmacological inhibition of SYK and ERK with specific phenotypic readout, single lab, multiple methods\",\n      \"pmids\": [\"39325623\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"A BTN2A1/BTN3A1 heterodimeric fusion protein provides 'signal 1' to activate Vγ9Vδ2+ T cells, but only in the presence of costimulatory signal via CD28 or NKG2D. A bispecific γδ T cell engager BTN2A1/3A1-Fc-CD19scFv alone enhanced granzyme B-mediated killing of CD19+ lymphoma cells when tumor cell costimulatory ligands satisfy 'signal 2'.\",\n      \"method\": \"Tumor cell-free T cell activation assay, cytotoxicity/granzyme B assay, heterodimeric fusion protein reconstitution\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional reconstitution with heterodimeric protein plus costimulatory dissection assays, single lab\",\n      \"pmids\": [\"36096643\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"19F solution NMR of BTN3A1 point mutants revealed that residues W421, T449, and T506 in the B30.2 domain undergo conformational/dynamic changes upon HMBPP and BTN2A1 association, while juxtamembrane residues T304 and G323 are not affected. W421 is located at the BTN2A1 binding interface (its mutation reduces BTN2A1 binding affinity), and T506 perturbation indicates a larger conformational change of the BTN3A1 B30.2 domain upon binding both HMBPP and BTN2A1.\",\n      \"method\": \"19F solution NMR, site-directed mutagenesis of BTN3A1, binding affinity measurements\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — rigorous NMR method but single lab, single study, no independent replication\",\n      \"pmids\": [\"40079188\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"BTN2A1 expression on lymphocytes increases via trogocytosis in the presence of activated myeloid cells (monocytes). BTN2A1-knockout B cells can acquire BTN2A1 from monocytes through trogocytosis, and BTN2A1-acquired normal or tumor cells exhibit higher sensitivity to Vγ9Vδ2 T cell lysis.\",\n      \"method\": \"BTN2A1 knockout cell lines, trogocytosis assay, cytotoxicity assay, flow cytometry\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — BTN2A1-KO reconstitution via trogocytosis with direct cytotoxicity readout, multiple methods, single lab\",\n      \"pmids\": [\"41066236\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Cryo-EM structures revealed that HMBPP (pAg) bridges the intracellular B30.2 domains of BTN3A1 and BTN2A1 in a full-length BTN3A1-BTN3A2-BTN2A1 complex. Upon TCR engagement, the BTN3A2-BTN2A1 ectodomain interaction dissociates, allowing BTN2A1 to bind the lateral surface of the Vγ9 chain while BTN3A2 binds the apical surface of the Vδ2 chain, supporting a 'pliers-like gripping' mechanism for TCR activation.\",\n      \"method\": \"Cryo-EM structural determination of full-length BTN complexes with and without TCR\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — cryo-EM structures (Tier 1 method) but preprint, not yet peer-reviewed, single study\",\n      \"pmids\": [\"bio_10.1101_2024.10.02.616253\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Single oncogenic mutations introduced into healthy colorectal or breast organoids are sufficient to upregulate surface-expressed BTN2A1 and enable Vγ9Vδ2 TCR binding to tumor cells. Full T cell activation additionally requires phosphorylation of juxtamembrane amino acids of BTN3A1, leading to activating heterodimerization of BTN2A1 and BTN3A1. Protein interactome mapping identified PHLDB2, SYNJ2, and CARMIL1 as key regulators of BTN2A1 and BTN3A1 surface dynamics during early malignant transformation.\",\n      \"method\": \"Genetically engineered step-wise mutagenesis organoid models, surface expression assays, Vγ9Vδ2 TCR binding assays, protein interactome mapping\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 2 / Weak — preprint, single study, novel interactors identified by interactome mapping without deep mechanistic validation of individual interactions\",\n      \"pmids\": [\"bio_10.1101_2024.11.19.624272\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The agonist antibody ICT01 (targeting BTN3As) destabilizes the BTN2A1-BTN3A interface and facilitates Vγ9Vδ2 TCR engagement, activating Vγ9Vδ2 T cells independently of phosphoantigens.\",\n      \"method\": \"Structural analysis, biochemical binding assays, cellular activation assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 2 / Weak — preprint, mechanistic claim about BTN2A1-BTN3A interface disruption supported by structural and biochemical data but not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.10.21.681109\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Metformin upregulates BTN3A1 and BTN2A1 expression on esophageal cancer cells in an AMPK-dependent manner, sensitizing them to Vγ9Vδ2 T cell-mediated cytotoxicity and granzyme B-mediated apoptosis.\",\n      \"method\": \"AMPK inhibitor experiments, surface expression assays, cytotoxicity assays, xenograft models\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — AMPK-dependence established by pharmacological inhibition with functional cytotoxicity readout, in vitro and in vivo xenograft confirmation, single lab\",\n      \"pmids\": [\"42248853\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"BTN2A1 is a cell-surface butyrophilin that functions as a direct ligand for the Vγ9 chain of the Vγ9Vδ2 TCR, forming a pAg-enhanced heterodimeric complex with BTN3A1 (and other BTN3A isoforms) at the cell surface—where intracellular HMBPP bridges the cytoplasmic B30.2 domains of BTN3A1 and BTN2A1, inducing conformational changes that allow BTN2A1 to engage the TCR and trigger γδ T cell cytotoxicity—while also acting as a DC-SIGN ligand through tumor-associated high-mannose glycosylation, and signaling through SYK/ERK in macrophages to regulate their polarization state.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"BTN2A1 is a cell-surface butyrophilin that serves as a direct, germline-encoded ligand for the Vγ9 chain of the Vγ9Vδ2 T cell receptor, functioning as the obligatory partner of BTN3A in phosphoantigen (pAg)-driven γδ T cell cytotoxicity against tumor cells [#0]. Co-expression of BTN2A1 with BTN3A1 is sufficient to trigger Vγ9Vδ2 TCR activation; BTN2A1 interacts with all three BTN3A isoforms, and this interaction is rate-limiting for BTN2A1 export to the plasma membrane [#0]. Phosphoantigen sensing operates through the intracellular B30.2 domains: HMBPP binds the B30.2 domain of BTN3A1, not BTN2A1, and bridges the two cytoplasmic domains, with BTN2A1 B30.2 homodimerization required for engagement of HMBPP-bound BTN3A1 [#3, #9]. At the cell surface the BTN2A1 and BTN3A IgV domains assemble in cis, but TCR and BTN3A1-IgV binding to BTN2A1-IgV are mutually exclusive, and pAg-induced conformational changes in the BTN3A1 B30.2 domain drive a rearrangement in which the BTN3A2–BTN2A1 ectodomain contact dissociates so that BTN2A1 engages the lateral surface of Vγ9 in a composite-ligand, 'pliers-like gripping' mechanism [#2, #7, #9]. Tumor-specific upregulation of surface BTN2A1 follows oncogenic transformation and can be induced pharmacologically through AMPK signaling, and agonist anti-BTN2A1 antibodies enhance γδ T cell killing and trigger caspase 3/7-mediated tumor pyroptosis [#4, #12]. Independently of γδ T cell recognition, BTN2A1 is a Ca2+-dependent ligand for DC-SIGN on immature dendritic cells via high-mannose glycans enriched on tumor cells, and antibody engagement of BTN2A1 on M2-like macrophages drives SYK- and ERK-dependent reprogramming toward an M1-like phenotype [#1, #5].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Before any γδ T cell role was known, BTN2A1 was first identified as a cell-surface glycoprotein ligand, establishing it as a glycan-dependent immune recognition molecule.\",\n      \"evidence\": \"Ig-fusion protein and DC-SIGN-transfectant binding assays with glycosylation analysis on dendritic cells\",\n      \"pmids\": [\"17785817\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not connect BTN2A1 to T cell biology or BTN3A\", \"Functional consequence of DC-SIGN engagement for DC differentiation not resolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Resolved the central question of what licenses BTN3A-mediated γδ T cell activation by identifying BTN2A1 as the required partner and a direct Vγ9Vδ2 TCR ligand.\",\n      \"evidence\": \"Cytotoxicity assays, co-expression reconstitution, antibody inhibition, and B30.2 domain mutagenesis in cancer cells\",\n      \"pmids\": [\"34260935\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular geometry of the BTN2A1/BTN3A/TCR assembly unresolved\", \"How pAg enhances the interaction not mechanistically defined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Established that BTN2A1/BTN3A1 provides 'signal 1' but requires costimulation, refining the requirements for productive γδ T cell engagement and enabling therapeutic engager design.\",\n      \"evidence\": \"Tumor cell-free activation assays with a BTN2A1/BTN3A1 heterodimeric fusion protein and CD28/NKG2D costimulation dissection\",\n      \"pmids\": [\"36096643\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry of the engineered heterodimer vs native complex unclear\", \"Costimulatory ligand requirements in primary tumors not mapped\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined the structural logic at the cell surface, showing TCR and BTN3A1-IgV binding to BTN2A1-IgV are mutually exclusive and supporting a composite-ligand model.\",\n      \"evidence\": \"NMR, structural modeling, mutagenesis, and TCR activation assays on IgV domains\",\n      \"pmids\": [\"36995939\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cis IgV interaction shown non-essential, leaving its biological purpose open\", \"Did not resolve the intracellular pAg-sensing step\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Localized pAg sensing to the intracellular domains, demonstrating HMBPP binds BTN3A1 (not BTN2A1) and that BTN2A1 B30.2 homodimerization is required to engage HMBPP-bound BTN3A1.\",\n      \"evidence\": \"Mutagenesis, size-exclusion chromatography, [31P]-NMR, ITC, and IFN-γ ELISA on internal-domain constructs\",\n      \"pmids\": [\"37171180\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How intracellular B30.2 engagement is transmitted to ectodomain rearrangement not shown\", \"Role of linker residues L318/L325 in full-length signaling untested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstrated BTN2A1 is a druggable target by showing agonist antibody engagement enhances γδ T cell killing and triggers tumor pyroptosis.\",\n      \"evidence\": \"Cytotoxicity, caspase 3/7, and holotomographic imaging assays with antibody 107G3B5 on tumor lines\",\n      \"pmids\": [\"39302336\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of agonism not biochemically reconstituted\", \"Pyroptotic pathway downstream of caspase activation not detailed\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended BTN2A1 function beyond γδ T cells, showing antibody engagement reprograms M2-like macrophages toward M1 via a defined SYK/ERK signaling cascade.\",\n      \"evidence\": \"Antibody treatment with SYK/ERK inhibitor experiments and ex vivo macrophage differentiation assays\",\n      \"pmids\": [\"39325623\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether native ligands drive this signaling, or only the antibody, is unknown\", \"Receptor proximal events linking BTN2A1 to SYK recruitment not defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Provided a full-length structural mechanism showing pAg bridges the intracellular B30.2 domains and TCR engagement drives ectodomain rearrangement into a 'pliers-like' grip.\",\n      \"evidence\": \"Cryo-EM of full-length BTN3A1-BTN3A2-BTN2A1 complexes with and without TCR (preprint)\",\n      \"pmids\": [\"bio_10.1101_2024.10.02.616253\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not peer-reviewed\", \"Dynamics of the transition state between cis and TCR-bound states not captured\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Linked BTN2A1 surface upregulation to oncogenic transformation and identified candidate regulators of its surface dynamics.\",\n      \"evidence\": \"Step-wise oncogenic mutagenesis in organoids with surface and interactome mapping (preprint)\",\n      \"pmids\": [\"bio_10.1101_2024.11.19.624272\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Preprint; PHLDB2/SYNJ2/CARMIL1 interactions identified by interactome mapping without mechanistic validation\", \"Causal link between specific oncogenic mutations and BTN2A1 induction not dissected\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Resolved which BTN3A1 B30.2 residues undergo pAg- and BTN2A1-induced conformational change, mapping the dynamic basis of binding.\",\n      \"evidence\": \"19F solution NMR of BTN3A1 point mutants with binding affinity measurements\",\n      \"pmids\": [\"40079188\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab, no independent replication\", \"Conformational changes in BTN2A1 itself not similarly mapped\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Showed BTN2A1 can be transferred between cells by trogocytosis, sensitizing recipient cells to γδ T cell lysis and expanding how BTN2A1 surface levels are regulated.\",\n      \"evidence\": \"BTN2A1-knockout cells, trogocytosis and cytotoxicity assays, flow cytometry\",\n      \"pmids\": [\"41066236\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo relevance of trogocytic transfer unproven\", \"Whether transferred BTN2A1 retains intracellular pAg-sensing capacity unaddressed\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Demonstrated a pharmacological route to enhance γδ T cell sensitivity by showing metformin upregulates BTN2A1/BTN3A1 via AMPK.\",\n      \"evidence\": \"AMPK inhibitor experiments, surface expression and cytotoxicity assays, xenograft models in esophageal cancer\",\n      \"pmids\": [\"42248853\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking AMPK to BTN transcription/surface trafficking not defined\", \"Effect generality across tumor types not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the intracellular pAg-induced B30.2 engagement is mechanically transmitted across the membrane to drive the ectodomain rearrangement that licenses BTN2A1–Vγ9 binding remains incompletely defined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No peer-reviewed full-length structure capturing the transition\", \"Surface trafficking regulators of BTN2A1 not mechanistically validated\", \"Physiological (non-antibody) triggers of BTN2A1 signaling in macrophages unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [0, 2, 9]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1, 9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 1, 5]}\n    ],\n    \"complexes\": [\"BTN2A1-BTN3A1-BTN3A2 phosphoantigen-sensing complex\"],\n    \"partners\": [\"BTN3A1\", \"BTN3A2\", \"BTN3A3\", \"DC-SIGN\", \"TRGV9\"]\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":6,"faith_total":6,"faith_pct":100.0}}