{"gene":"PVRIG","run_date":"2026-04-28T19:45:45","timeline":{"discoveries":[{"year":2016,"finding":"PVRIG (CD112R) is a coinhibitory receptor expressed on T cells that inhibits TCR-mediated signaling; CD112 (PVRL2/nectin-2) was identified as its high-affinity ligand, and PVRIG competes with CD226 (DNAM-1) to bind CD112. Disrupting the CD112R-CD112 interaction enhances human T cell responses.","method":"Binding assays, competition assays, T cell functional assays (receptor-mediated signaling inhibition)","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 — reciprocal binding/competition assays plus functional T cell readouts; foundational discovery paper, highly cited","pmids":["26755705"],"is_preprint":false},{"year":2019,"finding":"PVRIG acts as a coinhibitory receptor on CD8+ T cells that specifically binds PVRL2 (not PVR/CD155), and the PVRIG-PVRL2 pathway is nonredundant with the TIGIT-PVR pathway; PVRIG blockade increases CD8+ T cell cytokine production and cytotoxic activity, and combination with TIGIT or PD-1 blockade further enhances T cell activation.","method":"Binding specificity assays, CD8+ T cell functional assays (cytokine production, cytotoxicity), antibody blockade experiments in vitro and on tumor-infiltrating lymphocytes","journal":"Cancer immunology research","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (binding, functional T cell assays, primary TIL experiments), replicated across two companion papers","pmids":["30659054"],"is_preprint":false},{"year":2019,"finding":"Murine PVRIG binds PVRL2 strongly (its principal ligand) but interacts only weakly with PVR; PVRIG acts as an inducible coinhibitory receptor on CD8+ T cells that dampens antigen-specific effector responses. PVRIG-deficient CD8+ T cells mounted stronger effector responses during Listeria infection and showed enhanced anti-tumor function in vivo.","method":"Binding assays, PVRIG-knockout mouse studies, acute infection model (Listeria monocytogenes), syngeneic tumor models, anti-PVRIG antibody blockade","journal":"Cancer immunology research","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with defined phenotype plus in vivo tumor models, replicated across multiple approaches","pmids":["30659055"],"is_preprint":false},{"year":2017,"finding":"PVRIG (CD112R) is expressed on human NK cells and functions as an inhibitory receptor; blockade of CD112R (alone or combined with TIGIT blockade) enhances NK cell-mediated antibody-dependent cellular cytotoxicity (ADCC) triggered by trastuzumab against breast cancer cells.","method":"Flow cytometry for receptor expression on NK subsets, NK cell functional assays (ADCC), antibody blockade experiments","journal":"Cancer immunology, immunotherapy : CII","confidence":"Medium","confidence_rationale":"Tier 2 — clean functional assay with defined NK cell phenotype, single lab","pmids":["28623459"],"is_preprint":false},{"year":2021,"finding":"In AML, PVRIG is present at higher levels in the cytoplasm than on the NK cell surface, particularly in CD56bright NK cells; PVRIG is continually transported to the cell surface via the ER and Golgi in both unstimulated and activated NK cells. NK cell activation (by tumor recognition, cytokines IL-2/IL-12, or activating receptors CD16/NKp46) results in reduced PVRIG surface expression. PVRIG blockade enhances NK cell killing of PVRL2+ AML cells.","method":"Flow cytometry (surface vs. intracellular PVRIG), subcellular fractionation/trafficking assays (ER/Golgi transport), NK cell activation assays, cytotoxicity assays against AML blasts","journal":"Haematologica","confidence":"Medium","confidence_rationale":"Tier 2 — direct subcellular localization experiment with functional consequence, single lab but multiple orthogonal approaches","pmids":["33147937"],"is_preprint":false},{"year":2021,"finding":"PVRIG blockade in vivo inhibits exhaustion of NK cells and CD8+ T cells, slows tumor growth, and prolongs survival in murine tumor models; both NK and CD8+ T cells contribute to anti-tumor efficacy of PVRIG blockade, demonstrated by in vivo NK/CD8 T cell depletion. PVRIG blockade also showed therapeutic efficacy in the absence of adaptive immunity (Rag1-/- mice), highlighting a direct role on NK cells.","method":"PVRIG-knockout mice, in vivo depletion experiments (anti-NK/CD8 antibodies), Rag1-/- mouse model, syngeneic tumor models, human NK cell xenograft models","journal":"Journal of hematology & oncology","confidence":"High","confidence_rationale":"Tier 2 — genetic KO plus in vivo depletion with specific mechanistic readouts across multiple models","pmids":["34174928"],"is_preprint":false},{"year":2024,"finding":"Crystal structure of PVRIG in complex with Nectin-2 (PVRL2) revealed that PVRIG uses a unique CC' loop to engage Nectin-2 in a double-lock-and-key binding mode, achieving high-affinity interaction. Charged residues in the F-strands confer ligand selectivity for Nectin-2 but not Necl-5 (CD155/PVR).","method":"X-ray crystallography of PVRIG-Nectin-2 complex, mutagenesis to validate binding residues, comparative binding capacity measurements","journal":"Structure (London, England : 1993)","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with functional validation of key residues","pmids":["38626767"],"is_preprint":false},{"year":2024,"finding":"An anti-PVRIG antibody (IBI352g4a) with Fc-competent function blocks PVRIG-PVRL2 interaction and preferentially activates NK cells (inducing activation and degranulation) rather than T cells in vitro. In vivo, Fc effector function (FcγR engagement) was required for both NK cell activation and anti-tumor efficacy, demonstrating that both PVRIG checkpoint blockade and FcγR engagement are necessary for maximal antitumor effects.","method":"Binding affinity measurements (SPR/ELISA, Kd = 0.53 nM), in vitro NK and T cell functional assays, in vivo preclinical tumor models with mechanistic depletion analysis","journal":"Cancer immunology, immunotherapy : CII","confidence":"Medium","confidence_rationale":"Tier 2 — in vitro and in vivo mechanistic dissection with Fc-variant antibodies, single lab","pmids":["38554184"],"is_preprint":false},{"year":2024,"finding":"PVRL2 deletion in syngeneic mouse tumor models suppressed tumor growth even in the absence of PVRIG, indicating that PVRL2 has PVRIG-independent inhibitory mechanisms on CD8+ T and NK cells. PVRIG loss showed no additive effect in the absence of PVRL2, placing PVRIG strictly downstream of PVRL2 in this signaling axis.","method":"PVRL2-knockout and PVRIG-knockout syngeneic mouse tumor models, epistasis analysis (double KO), immune cell depletion experiments","journal":"Cancer immunology research","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis across multiple syngeneic models with clean double-KO controls","pmids":["38588410"],"is_preprint":false}],"current_model":"PVRIG (CD112R) is an inhibitory immune checkpoint receptor expressed on T and NK cells that binds with high affinity and selectivity to PVRL2 (Nectin-2/CD112) — but not PVR/CD155 — via a unique CC' loop and charged F-strand residues revealed by crystal structure; upon PVRL2 engagement, PVRIG delivers inhibitory signals that suppress TCR-mediated T cell activation and NK cell cytotoxicity, competing with the activating receptor CD226 for CD112 binding; PVRIG is constitutively trafficked from the ER/Golgi to the cell surface where it undergoes rapid turnover, with surface levels decreasing upon NK cell activation; PVRIG acts as an inducible checkpoint strictly downstream of PVRL2 in the tumor microenvironment, and its blockade — particularly when combined with TIGIT or PD-1 pathway inhibition — enhances CD8+ T and NK cell effector function and reduces tumor growth in preclinical models."},"narrative":{"teleology":[{"year":2016,"claim":"Identification of PVRIG as a coinhibitory receptor and PVRL2 as its ligand established a new checkpoint axis competing with the activating receptor CD226 for the same ligand.","evidence":"Binding assays, competition assays, and T cell functional assays in human cells","pmids":["26755705"],"confidence":"High","gaps":["Signaling pathway downstream of PVRIG engagement not defined","Relevance to NK cells not yet tested","In vivo role in tumor immunity unknown"]},{"year":2017,"claim":"Demonstrating PVRIG expression and inhibitory function on NK cells extended the receptor's role beyond T cells and showed combinatorial benefit with TIGIT blockade for enhancing ADCC.","evidence":"Flow cytometry for NK subset expression, NK-mediated ADCC assays with trastuzumab against breast cancer cells","pmids":["28623459"],"confidence":"Medium","gaps":["Single-lab study without in vivo validation of NK-specific blockade","Whether PVRIG signals via ITIM or other motifs on NK cells not addressed","Ligand specificity on NK cells not formally tested"]},{"year":2019,"claim":"Establishing that PVRIG binds selectively to PVRL2 (not PVR) and is nonredundant with TIGIT-PVR demonstrated two parallel, independent inhibitory axes within the nectin/nectin-like receptor family, with combinatorial blockade yielding additive benefit.","evidence":"Binding specificity assays, CD8+ T cell functional assays, antibody blockade on primary TILs, PVRIG-KO mice in infection and tumor models","pmids":["30659054","30659055"],"confidence":"High","gaps":["Intracellular signaling mechanism of PVRIG still undefined","Whether PVRIG contributes to T cell exhaustion programs not resolved","Role in human tumors beyond ex vivo TIL experiments not established"]},{"year":2021,"claim":"Subcellular trafficking studies revealed that PVRIG is constitutively shuttled from the ER/Golgi to the NK cell surface and undergoes activation-induced downregulation, explaining why surface levels are dynamically regulated in the tumor microenvironment.","evidence":"Surface versus intracellular flow cytometry, subcellular fractionation/ER-Golgi trafficking assays, NK cell activation assays against AML blasts","pmids":["33147937"],"confidence":"Medium","gaps":["Single-lab study; mechanism of activation-induced internalization or degradation not identified","Whether trafficking regulation occurs similarly in T cells not tested","Ubiquitination or other post-translational modifications governing turnover unknown"]},{"year":2021,"claim":"In vivo depletion and Rag1-deficient experiments demonstrated that PVRIG blockade acts directly on both NK cells and CD8+ T cells to inhibit exhaustion and slow tumor growth, resolving the cellular mediators of therapeutic efficacy.","evidence":"PVRIG-KO mice, in vivo NK/CD8 depletion, Rag1−/− models, syngeneic and human xenograft tumor models","pmids":["34174928"],"confidence":"High","gaps":["Molecular definition of how PVRIG drives exhaustion programs absent","Contribution of CD4+ T cells or other immune subsets not assessed","Human in vivo efficacy not yet demonstrated"]},{"year":2024,"claim":"The crystal structure of the PVRIG–Nectin-2 complex revealed the structural basis for ligand selectivity: a unique CC' loop and charged F-strand residues create a double-lock-and-key interface that excludes PVR binding.","evidence":"X-ray crystallography of the PVRIG–Nectin-2 complex with mutagenesis validation","pmids":["38626767"],"confidence":"High","gaps":["No structural information on how PVRIG cytoplasmic domain engages signaling mediators","Whether the CC' loop interface can be targeted by small molecules not explored","Dynamics of receptor oligomerization at the cell surface unknown"]},{"year":2024,"claim":"Genetic epistasis showed PVRIG functions strictly downstream of PVRL2 and that PVRL2 possesses PVRIG-independent inhibitory functions, refining the hierarchy of the PVRL2 signaling axis in tumor immunity.","evidence":"PVRL2-KO, PVRIG-KO, and double-KO syngeneic tumor models with immune cell depletion","pmids":["38588410"],"confidence":"High","gaps":["Identity of the PVRIG-independent inhibitory receptor(s) for PVRL2 not determined","Whether epistatic relationship holds in human tumors unknown","Relevance in immunologically cold tumor types not tested"]},{"year":2024,"claim":"Therapeutic dissection of an anti-PVRIG antibody showed that both checkpoint blockade and FcγR-mediated effector function are required for maximal NK cell activation and antitumor efficacy, informing optimal antibody design.","evidence":"SPR/ELISA binding, Fc-variant antibody comparison, in vitro NK/T cell assays, in vivo tumor models","pmids":["38554184"],"confidence":"Medium","gaps":["Single-lab finding; independent replication with different Fc-engineered antibodies needed","Mechanism of FcγR-dependent NK activation (co-stimulatory vs. ADCC-like) not fully dissected","Optimal combination partners in human trials remain undefined"]},{"year":null,"claim":"The intracellular signaling pathway activated by PVRIG engagement — including its proximal signaling mediators, ITIM/ITSM utilization, and transcriptional consequences — remains undefined.","evidence":"","pmids":[],"confidence":"Low","gaps":["No phosphoproteomics or proximal signaling analysis reported","Relationship between PVRIG signaling and T cell exhaustion transcriptional programs uncharacterized","No structural data on the PVRIG cytoplasmic domain or its adaptor interactions"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,2,3]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3,4]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[4]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[4]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,1,2,3,5]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,8]}],"complexes":[],"partners":["PVRL2","CD226","TIGIT"],"other_free_text":[]},"mechanistic_narrative":"PVRIG (CD112R) is an inhibitory immune checkpoint receptor on T cells and NK cells that suppresses antitumor and antigen-specific effector responses by engaging its high-affinity ligand PVRL2 (Nectin-2/CD112). PVRIG binds PVRL2 — but not PVR/CD155 — through a unique CC' loop and charged F-strand residues that form a double-lock-and-key interface, competing with the activating receptor CD226 for PVRL2 access [PMID:26755705, PMID:38626767]. Genetic epistasis experiments place PVRIG strictly downstream of PVRL2 in the tumor microenvironment; PVRIG-deficient CD8+ T cells and NK cells mount stronger effector responses, and PVRIG blockade — especially combined with TIGIT or PD-1 pathway inhibition — enhances cytotoxicity and reduces tumor growth in vivo [PMID:30659055, PMID:34174928, PMID:38588410]. On NK cells, PVRIG is constitutively trafficked from the ER/Golgi to the cell surface where it undergoes rapid turnover, with surface levels decreasing upon activation [PMID:33147937]."},"prefetch_data":{"uniprot":{"accession":"Q6DKI7","full_name":"Transmembrane protein PVRIG","aliases":["CD112 receptor","CD112R","Poliovirus receptor-related immunoglobulin domain-containing protein"],"length_aa":326,"mass_kda":34.3,"function":"Cell surface receptor for NECTIN2. May act as a coinhibitory receptor that suppresses T-cell receptor-mediated signals. Following interaction with NECTIN2, inhibits T-cell proliferation. Competes with CD226 for NECTIN2-binding","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q6DKI7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PVRIG","classification":"Not Classified","n_dependent_lines":20,"n_total_lines":1208,"dependency_fraction":0.016556291390728478},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PVRIG","total_profiled":1310},"omim":[{"mim_id":"617012","title":"POLIOVIRUS RECEPTOR-RELATED IMMUNOGLOBULIN DOMAIN-CONTAINING PROTEIN; PVRIG","url":"https://www.omim.org/entry/617012"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"lymphoid tissue","ntpm":44.5}],"url":"https://www.proteinatlas.org/search/PVRIG"},"hgnc":{"alias_symbol":["MGC2463","C7orf15","CD112R"],"prev_symbol":[]},"alphafold":{"accession":"Q6DKI7","domains":[{"cath_id":"2.60.40.10","chopping":"44-153","consensus_level":"high","plddt":82.8835,"start":44,"end":153}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q6DKI7","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q6DKI7-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q6DKI7-F1-predicted_aligned_error_v6.png","plddt_mean":60.84},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PVRIG","jax_strain_url":"https://www.jax.org/strain/search?query=PVRIG"},"sequence":{"accession":"Q6DKI7","fasta_url":"https://rest.uniprot.org/uniprotkb/Q6DKI7.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q6DKI7/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q6DKI7"}},"corpus_meta":[{"pmid":"31234588","id":"PMC_31234588","title":"DNAM-1 and the TIGIT/PVRIG/TACTILE Axis: Novel Immune Checkpoints for Natural Killer Cell-Based Cancer Immunotherapy.","date":"2019","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/31234588","citation_count":174,"is_preprint":false},{"pmid":"26755705","id":"PMC_26755705","title":"Identification of CD112R as a novel checkpoint for human T cells.","date":"2016","source":"The Journal of experimental medicine","url":"https://pubmed.ncbi.nlm.nih.gov/26755705","citation_count":174,"is_preprint":false},{"pmid":"30659054","id":"PMC_30659054","title":"PVRIG and PVRL2 Are Induced in Cancer and Inhibit CD8+ T-cell Function.","date":"2019","source":"Cancer immunology research","url":"https://pubmed.ncbi.nlm.nih.gov/30659054","citation_count":134,"is_preprint":false},{"pmid":"28623459","id":"PMC_28623459","title":"Blockade of CD112R and TIGIT signaling sensitizes human natural killer cell functions.","date":"2017","source":"Cancer immunology, immunotherapy : CII","url":"https://pubmed.ncbi.nlm.nih.gov/28623459","citation_count":125,"is_preprint":false},{"pmid":"30659055","id":"PMC_30659055","title":"Mouse PVRIG Has CD8+ T Cell-Specific Coinhibitory Functions and Dampens Antitumor Immunity.","date":"2019","source":"Cancer immunology research","url":"https://pubmed.ncbi.nlm.nih.gov/30659055","citation_count":47,"is_preprint":false},{"pmid":"34507594","id":"PMC_34507594","title":"The CD112R/CD112 axis: a breakthrough in cancer immunotherapy.","date":"2021","source":"Journal of experimental & clinical cancer research : CR","url":"https://pubmed.ncbi.nlm.nih.gov/34507594","citation_count":46,"is_preprint":false},{"pmid":"33298247","id":"PMC_33298247","title":"Hitting the complexity of the TIGIT-CD96-CD112R-CD226 axis for next-generation cancer immunotherapy.","date":"2021","source":"BMB reports","url":"https://pubmed.ncbi.nlm.nih.gov/33298247","citation_count":44,"is_preprint":false},{"pmid":"34174928","id":"PMC_34174928","title":"Blockade of checkpoint receptor PVRIG unleashes anti-tumor immunity of NK cells in murine and human solid tumors.","date":"2021","source":"Journal of hematology & oncology","url":"https://pubmed.ncbi.nlm.nih.gov/34174928","citation_count":42,"is_preprint":false},{"pmid":"33903974","id":"PMC_33903974","title":"COM902, a novel therapeutic antibody targeting TIGIT augments anti-tumor T cell function in combination with PVRIG or PD-1 pathway blockade.","date":"2021","source":"Cancer immunology, immunotherapy : CII","url":"https://pubmed.ncbi.nlm.nih.gov/33903974","citation_count":34,"is_preprint":false},{"pmid":"33147937","id":"PMC_33147937","title":"PVRIG is a novel natural killer cell immune checkpoint receptor in acute myeloid leukemia.","date":"2021","source":"Haematologica","url":"https://pubmed.ncbi.nlm.nih.gov/33147937","citation_count":26,"is_preprint":false},{"pmid":"38588410","id":"PMC_38588410","title":"PVRL2 Suppresses Antitumor Immunity through PVRIG- and TIGIT-independent Pathways.","date":"2024","source":"Cancer immunology research","url":"https://pubmed.ncbi.nlm.nih.gov/38588410","citation_count":10,"is_preprint":false},{"pmid":"36788088","id":"PMC_36788088","title":"Nonredundant Upregulation of CD112R (PVRIG) and PD-1 on Cytotoxic T Lymphocytes Located in T Cell Nests of Colorectal Cancer.","date":"2023","source":"Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc","url":"https://pubmed.ncbi.nlm.nih.gov/36788088","citation_count":10,"is_preprint":false},{"pmid":"39851063","id":"PMC_39851063","title":"Co-blocking TIGIT and PVRIG Using a Novel Bispecific Antibody Enhances Antitumor Immunity.","date":"2025","source":"Molecular cancer therapeutics","url":"https://pubmed.ncbi.nlm.nih.gov/39851063","citation_count":5,"is_preprint":false},{"pmid":"38626767","id":"PMC_38626767","title":"Structural basis for the immune recognition and selectivity of the immune receptor PVRIG for ligand Nectin-2.","date":"2024","source":"Structure (London, England : 1993)","url":"https://pubmed.ncbi.nlm.nih.gov/38626767","citation_count":5,"is_preprint":false},{"pmid":"38554184","id":"PMC_38554184","title":"Characterization of a novel anti-PVRIG antibody with Fc-competent function that exerts strong antitumor effects via NK activation in preclinical models.","date":"2024","source":"Cancer immunology, immunotherapy : CII","url":"https://pubmed.ncbi.nlm.nih.gov/38554184","citation_count":3,"is_preprint":false},{"pmid":"40425968","id":"PMC_40425968","title":"Investigation of TIGIT, PVRIG, CD112 and CD155 expression in early and late onset preeclampsia.","date":"2025","source":"Journal of molecular histology","url":"https://pubmed.ncbi.nlm.nih.gov/40425968","citation_count":0,"is_preprint":false},{"pmid":"39694409","id":"PMC_39694409","title":"The inhibitory receptor PVRIG is dominantly expressed in the bone marrow of patients with multiple myeloma and its blockade enhances T-cell engager's immune activation.","date":"2024","source":"Experimental hematology","url":"https://pubmed.ncbi.nlm.nih.gov/39694409","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.02.19.25322384","title":"Downregulation of cancer hallmarks and immune check-points in patients with glioblastoma following a short course of the pro-oxidant combination of Resveratrol and Copper","date":"2025-02-24","source":"bioRxiv","url":"https://doi.org/10.1101/2025.02.19.25322384","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.01.16.633312","title":"Epigenetic Modulation of Host Immunity related genes in Pulmonary Tuberculosis: A Comprehensive Analysis of DNA Methylation Profiles in Peripheral Blood Mononuclear Cells","date":"2025-01-18","source":"bioRxiv","url":"https://doi.org/10.1101/2025.01.16.633312","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11219,"output_tokens":2443,"usd":0.035151},"stage2":{"model":"claude-opus-4-6","input_tokens":5755,"output_tokens":2309,"usd":0.12975},"total_usd":0.164901,"stage1_batch_id":"msgbatch_01SUR8NDzVrNmyszWyJeCct7","stage2_batch_id":"msgbatch_01G7Yfutko3cDWzejrwH5AMx","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2016,\n      \"finding\": \"PVRIG (CD112R) is a coinhibitory receptor expressed on T cells that inhibits TCR-mediated signaling; CD112 (PVRL2/nectin-2) was identified as its high-affinity ligand, and PVRIG competes with CD226 (DNAM-1) to bind CD112. Disrupting the CD112R-CD112 interaction enhances human T cell responses.\",\n      \"method\": \"Binding assays, competition assays, T cell functional assays (receptor-mediated signaling inhibition)\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal binding/competition assays plus functional T cell readouts; foundational discovery paper, highly cited\",\n      \"pmids\": [\"26755705\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PVRIG acts as a coinhibitory receptor on CD8+ T cells that specifically binds PVRL2 (not PVR/CD155), and the PVRIG-PVRL2 pathway is nonredundant with the TIGIT-PVR pathway; PVRIG blockade increases CD8+ T cell cytokine production and cytotoxic activity, and combination with TIGIT or PD-1 blockade further enhances T cell activation.\",\n      \"method\": \"Binding specificity assays, CD8+ T cell functional assays (cytokine production, cytotoxicity), antibody blockade experiments in vitro and on tumor-infiltrating lymphocytes\",\n      \"journal\": \"Cancer immunology research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (binding, functional T cell assays, primary TIL experiments), replicated across two companion papers\",\n      \"pmids\": [\"30659054\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Murine PVRIG binds PVRL2 strongly (its principal ligand) but interacts only weakly with PVR; PVRIG acts as an inducible coinhibitory receptor on CD8+ T cells that dampens antigen-specific effector responses. PVRIG-deficient CD8+ T cells mounted stronger effector responses during Listeria infection and showed enhanced anti-tumor function in vivo.\",\n      \"method\": \"Binding assays, PVRIG-knockout mouse studies, acute infection model (Listeria monocytogenes), syngeneic tumor models, anti-PVRIG antibody blockade\",\n      \"journal\": \"Cancer immunology research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with defined phenotype plus in vivo tumor models, replicated across multiple approaches\",\n      \"pmids\": [\"30659055\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PVRIG (CD112R) is expressed on human NK cells and functions as an inhibitory receptor; blockade of CD112R (alone or combined with TIGIT blockade) enhances NK cell-mediated antibody-dependent cellular cytotoxicity (ADCC) triggered by trastuzumab against breast cancer cells.\",\n      \"method\": \"Flow cytometry for receptor expression on NK subsets, NK cell functional assays (ADCC), antibody blockade experiments\",\n      \"journal\": \"Cancer immunology, immunotherapy : CII\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean functional assay with defined NK cell phenotype, single lab\",\n      \"pmids\": [\"28623459\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In AML, PVRIG is present at higher levels in the cytoplasm than on the NK cell surface, particularly in CD56bright NK cells; PVRIG is continually transported to the cell surface via the ER and Golgi in both unstimulated and activated NK cells. NK cell activation (by tumor recognition, cytokines IL-2/IL-12, or activating receptors CD16/NKp46) results in reduced PVRIG surface expression. PVRIG blockade enhances NK cell killing of PVRL2+ AML cells.\",\n      \"method\": \"Flow cytometry (surface vs. intracellular PVRIG), subcellular fractionation/trafficking assays (ER/Golgi transport), NK cell activation assays, cytotoxicity assays against AML blasts\",\n      \"journal\": \"Haematologica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct subcellular localization experiment with functional consequence, single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"33147937\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PVRIG blockade in vivo inhibits exhaustion of NK cells and CD8+ T cells, slows tumor growth, and prolongs survival in murine tumor models; both NK and CD8+ T cells contribute to anti-tumor efficacy of PVRIG blockade, demonstrated by in vivo NK/CD8 T cell depletion. PVRIG blockade also showed therapeutic efficacy in the absence of adaptive immunity (Rag1-/- mice), highlighting a direct role on NK cells.\",\n      \"method\": \"PVRIG-knockout mice, in vivo depletion experiments (anti-NK/CD8 antibodies), Rag1-/- mouse model, syngeneic tumor models, human NK cell xenograft models\",\n      \"journal\": \"Journal of hematology & oncology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO plus in vivo depletion with specific mechanistic readouts across multiple models\",\n      \"pmids\": [\"34174928\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Crystal structure of PVRIG in complex with Nectin-2 (PVRL2) revealed that PVRIG uses a unique CC' loop to engage Nectin-2 in a double-lock-and-key binding mode, achieving high-affinity interaction. Charged residues in the F-strands confer ligand selectivity for Nectin-2 but not Necl-5 (CD155/PVR).\",\n      \"method\": \"X-ray crystallography of PVRIG-Nectin-2 complex, mutagenesis to validate binding residues, comparative binding capacity measurements\",\n      \"journal\": \"Structure (London, England : 1993)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with functional validation of key residues\",\n      \"pmids\": [\"38626767\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"An anti-PVRIG antibody (IBI352g4a) with Fc-competent function blocks PVRIG-PVRL2 interaction and preferentially activates NK cells (inducing activation and degranulation) rather than T cells in vitro. In vivo, Fc effector function (FcγR engagement) was required for both NK cell activation and anti-tumor efficacy, demonstrating that both PVRIG checkpoint blockade and FcγR engagement are necessary for maximal antitumor effects.\",\n      \"method\": \"Binding affinity measurements (SPR/ELISA, Kd = 0.53 nM), in vitro NK and T cell functional assays, in vivo preclinical tumor models with mechanistic depletion analysis\",\n      \"journal\": \"Cancer immunology, immunotherapy : CII\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro and in vivo mechanistic dissection with Fc-variant antibodies, single lab\",\n      \"pmids\": [\"38554184\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PVRL2 deletion in syngeneic mouse tumor models suppressed tumor growth even in the absence of PVRIG, indicating that PVRL2 has PVRIG-independent inhibitory mechanisms on CD8+ T and NK cells. PVRIG loss showed no additive effect in the absence of PVRL2, placing PVRIG strictly downstream of PVRL2 in this signaling axis.\",\n      \"method\": \"PVRL2-knockout and PVRIG-knockout syngeneic mouse tumor models, epistasis analysis (double KO), immune cell depletion experiments\",\n      \"journal\": \"Cancer immunology research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis across multiple syngeneic models with clean double-KO controls\",\n      \"pmids\": [\"38588410\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PVRIG (CD112R) is an inhibitory immune checkpoint receptor expressed on T and NK cells that binds with high affinity and selectivity to PVRL2 (Nectin-2/CD112) — but not PVR/CD155 — via a unique CC' loop and charged F-strand residues revealed by crystal structure; upon PVRL2 engagement, PVRIG delivers inhibitory signals that suppress TCR-mediated T cell activation and NK cell cytotoxicity, competing with the activating receptor CD226 for CD112 binding; PVRIG is constitutively trafficked from the ER/Golgi to the cell surface where it undergoes rapid turnover, with surface levels decreasing upon NK cell activation; PVRIG acts as an inducible checkpoint strictly downstream of PVRL2 in the tumor microenvironment, and its blockade — particularly when combined with TIGIT or PD-1 pathway inhibition — enhances CD8+ T and NK cell effector function and reduces tumor growth in preclinical models.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PVRIG (CD112R) is an inhibitory immune checkpoint receptor on T cells and NK cells that suppresses antitumor and antigen-specific effector responses by engaging its high-affinity ligand PVRL2 (Nectin-2/CD112). PVRIG binds PVRL2 — but not PVR/CD155 — through a unique CC' loop and charged F-strand residues that form a double-lock-and-key interface, competing with the activating receptor CD226 for PVRL2 access [PMID:26755705, PMID:38626767]. Genetic epistasis experiments place PVRIG strictly downstream of PVRL2 in the tumor microenvironment; PVRIG-deficient CD8+ T cells and NK cells mount stronger effector responses, and PVRIG blockade — especially combined with TIGIT or PD-1 pathway inhibition — enhances cytotoxicity and reduces tumor growth in vivo [PMID:30659055, PMID:34174928, PMID:38588410]. On NK cells, PVRIG is constitutively trafficked from the ER/Golgi to the cell surface where it undergoes rapid turnover, with surface levels decreasing upon activation [PMID:33147937].\",\n  \"teleology\": [\n    {\n      \"year\": 2016,\n      \"claim\": \"Identification of PVRIG as a coinhibitory receptor and PVRL2 as its ligand established a new checkpoint axis competing with the activating receptor CD226 for the same ligand.\",\n      \"evidence\": \"Binding assays, competition assays, and T cell functional assays in human cells\",\n      \"pmids\": [\"26755705\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Signaling pathway downstream of PVRIG engagement not defined\",\n        \"Relevance to NK cells not yet tested\",\n        \"In vivo role in tumor immunity unknown\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrating PVRIG expression and inhibitory function on NK cells extended the receptor's role beyond T cells and showed combinatorial benefit with TIGIT blockade for enhancing ADCC.\",\n      \"evidence\": \"Flow cytometry for NK subset expression, NK-mediated ADCC assays with trastuzumab against breast cancer cells\",\n      \"pmids\": [\"28623459\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single-lab study without in vivo validation of NK-specific blockade\",\n        \"Whether PVRIG signals via ITIM or other motifs on NK cells not addressed\",\n        \"Ligand specificity on NK cells not formally tested\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Establishing that PVRIG binds selectively to PVRL2 (not PVR) and is nonredundant with TIGIT-PVR demonstrated two parallel, independent inhibitory axes within the nectin/nectin-like receptor family, with combinatorial blockade yielding additive benefit.\",\n      \"evidence\": \"Binding specificity assays, CD8+ T cell functional assays, antibody blockade on primary TILs, PVRIG-KO mice in infection and tumor models\",\n      \"pmids\": [\"30659054\", \"30659055\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Intracellular signaling mechanism of PVRIG still undefined\",\n        \"Whether PVRIG contributes to T cell exhaustion programs not resolved\",\n        \"Role in human tumors beyond ex vivo TIL experiments not established\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Subcellular trafficking studies revealed that PVRIG is constitutively shuttled from the ER/Golgi to the NK cell surface and undergoes activation-induced downregulation, explaining why surface levels are dynamically regulated in the tumor microenvironment.\",\n      \"evidence\": \"Surface versus intracellular flow cytometry, subcellular fractionation/ER-Golgi trafficking assays, NK cell activation assays against AML blasts\",\n      \"pmids\": [\"33147937\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single-lab study; mechanism of activation-induced internalization or degradation not identified\",\n        \"Whether trafficking regulation occurs similarly in T cells not tested\",\n        \"Ubiquitination or other post-translational modifications governing turnover unknown\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"In vivo depletion and Rag1-deficient experiments demonstrated that PVRIG blockade acts directly on both NK cells and CD8+ T cells to inhibit exhaustion and slow tumor growth, resolving the cellular mediators of therapeutic efficacy.\",\n      \"evidence\": \"PVRIG-KO mice, in vivo NK/CD8 depletion, Rag1−/− models, syngeneic and human xenograft tumor models\",\n      \"pmids\": [\"34174928\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Molecular definition of how PVRIG drives exhaustion programs absent\",\n        \"Contribution of CD4+ T cells or other immune subsets not assessed\",\n        \"Human in vivo efficacy not yet demonstrated\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"The crystal structure of the PVRIG–Nectin-2 complex revealed the structural basis for ligand selectivity: a unique CC' loop and charged F-strand residues create a double-lock-and-key interface that excludes PVR binding.\",\n      \"evidence\": \"X-ray crystallography of the PVRIG–Nectin-2 complex with mutagenesis validation\",\n      \"pmids\": [\"38626767\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No structural information on how PVRIG cytoplasmic domain engages signaling mediators\",\n        \"Whether the CC' loop interface can be targeted by small molecules not explored\",\n        \"Dynamics of receptor oligomerization at the cell surface unknown\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Genetic epistasis showed PVRIG functions strictly downstream of PVRL2 and that PVRL2 possesses PVRIG-independent inhibitory functions, refining the hierarchy of the PVRL2 signaling axis in tumor immunity.\",\n      \"evidence\": \"PVRL2-KO, PVRIG-KO, and double-KO syngeneic tumor models with immune cell depletion\",\n      \"pmids\": [\"38588410\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Identity of the PVRIG-independent inhibitory receptor(s) for PVRL2 not determined\",\n        \"Whether epistatic relationship holds in human tumors unknown\",\n        \"Relevance in immunologically cold tumor types not tested\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Therapeutic dissection of an anti-PVRIG antibody showed that both checkpoint blockade and FcγR-mediated effector function are required for maximal NK cell activation and antitumor efficacy, informing optimal antibody design.\",\n      \"evidence\": \"SPR/ELISA binding, Fc-variant antibody comparison, in vitro NK/T cell assays, in vivo tumor models\",\n      \"pmids\": [\"38554184\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single-lab finding; independent replication with different Fc-engineered antibodies needed\",\n        \"Mechanism of FcγR-dependent NK activation (co-stimulatory vs. ADCC-like) not fully dissected\",\n        \"Optimal combination partners in human trials remain undefined\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The intracellular signaling pathway activated by PVRIG engagement — including its proximal signaling mediators, ITIM/ITSM utilization, and transcriptional consequences — remains undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No phosphoproteomics or proximal signaling analysis reported\",\n        \"Relationship between PVRIG signaling and T cell exhaustion transcriptional programs uncharacterized\",\n        \"No structural data on the PVRIG cytoplasmic domain or its adaptor interactions\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 2, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3, 4]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 1, 2, 3, 5]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 8]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"PVRL2\",\n      \"CD226\",\n      \"TIGIT\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}