{"gene":"CEACAM8","run_date":"2026-06-09T22:57:18","timeline":{"discoveries":[{"year":1996,"finding":"CD66b (CEACAM8) antibody binding to neutrophils triggers a transient calcium-dependent activation signal that upregulates CD11/CD18 on the neutrophil surface and increases neutrophil adhesion to HUVEC monolayers; this response requires physiological extracellular calcium at or near the time of antibody binding, and CD66b can independently transmit signals in neutrophils as shown by sequential desensitization experiments.","method":"Functional adhesion assay with CD66 mAbs, calcium chelation experiments, sequential desensitization, flow cytometry","journal":"Journal of leukocyte biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal functional assays (adhesion, desensitization, calcium requirement) in single lab","pmids":["8699114"],"is_preprint":false},{"year":1992,"finding":"CD66b (CGM6/NCA-95) is a GPI-anchored glycoprotein of ~100 kDa on granulocyte surfaces; it can be released by phosphatidylinositol-specific phospholipase C, and its deglycosylated core is ~38 kDa, consistent with the CGM6-encoded protein.","method":"Immunoprecipitation, SDS-PAGE, PI-PLC cleavage, immunoblotting with anti-CD67 and anti-NCA antibodies","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct biochemical demonstration of GPI anchor (PI-PLC release), molecular weight characterization, and antibody cross-reactivity with recombinant CGM6 protein","pmids":["1370882"],"is_preprint":false},{"year":1996,"finding":"CD66b (CGM6) mediates heterophilic cell adhesion with CD66c (NCA); this interaction occurs via the N-terminal domains of both molecules and does not require the carbohydrate portions, as deglycosylated recombinant proteins retain adhesion activity. Activated neutrophils adhere to immobilized CD66b, and this adhesion induces superoxide anion release.","method":"Soluble recombinant protein binding assay, deglycosylation, CHO transfectant adhesion, N-domain antibody inhibition, superoxide anion assay","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted adhesion with recombinant proteins, deglycosylation control, domain-blocking antibodies, and functional superoxide readout in single study","pmids":["8645267"],"is_preprint":false},{"year":1999,"finding":"CD66b is stored in gelatinase and specific granules of resting neutrophils and mobilized to the cell surface upon activation; it was identified as one of two major galectin-3 receptors on neutrophils (alongside CD66a) by galectin-3-Sepharose affinity chromatography of granule contents, with the ~100 kDa eluted band confirmed as CD66b by immunoblotting.","method":"Galectin-3-Sepharose affinity chromatography, SDS-PAGE, immunoblotting, subcellular fractionation of neutrophil granules, HL-60 differentiation model","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct biochemical purification from native granule fractions, immunoblot confirmation, functional validation using HL-60 cells lacking specific/gelatinase granules","pmids":["10553088"],"is_preprint":false},{"year":2001,"finding":"The N-terminal domain (N-domain) of CEACAM8 (CD66b) mediates heterophilic adhesion to CEACAM6 (CD66c). By homologue-scanning mutagenesis of CHO transfectants expressing chimeric/mutant proteins, critical residues for CEACAM6–CEACAM8 heterophilic adhesion were mapped; these overlap with, but are not identical to, residues required for CEACAM6 homophilic adhesion and Neisseria Opa protein binding.","method":"CHO transfectant adhesion assay, homologue-scanning mutagenesis, chimeric protein expression","journal":"Journal of leukocyte biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — systematic mutagenesis with functional readout in reconstituted cell-adhesion system","pmids":["11590190"],"is_preprint":false},{"year":2007,"finding":"CD66b (CEACAM8) on human eosinophils is localized in lipid rafts and is constitutively and physically associated with the β2 integrin CD11b. Engagement of CD66b by mAb or its natural ligand galectin-3 activates the Src-family kinase Hck and induces cellular adhesion, superoxide production, and degranulation. Cross-linking of CD66b causes striking clustering of CD11b. Disruption of lipid rafts or removal of the GPI anchor inhibits these responses.","method":"Co-immunoprecipitation, lipid raft fractionation, GPI anchor removal, mAb cross-linking, superoxide assay, degranulation assay, confocal microscopy","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (co-IP, raft disruption, GPI removal, functional assays) in a single study establishing mechanism","pmids":["18056392"],"is_preprint":false},{"year":2006,"finding":"Cross-linking of CD66b on peripheral blood neutrophils induces release of pre-stored interleukin-8 (IL-8) from intracellular storage without de novo synthesis, in contrast to LPS stimulation which drives de novo cytokine synthesis.","method":"CD66b cross-linking with mAb, ELISA for IL-8, comparison with LPS-stimulated de novo synthesis","journal":"Human immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional assay with cross-linking and comparison condition; single lab, two orthogonal methods (ELISA + cross-linking)","pmids":["17002897"],"is_preprint":false},{"year":1999,"finding":"CD66b (GPI-anchored) and CD11b/CD18 undergo lectin-like physical interactions on the neutrophil surface; cross-linking of CD66b redistributes CD11b into discrete clusters via a D-mannose-sensitive process. CD66b is required for neutrophil cytolytic activity in GM-CSF/Lym-1-mediated antibody-dependent cytolysis, as shown by inhibitory anti-CD66b mAb.","method":"Immunofluorescence redistribution assay, D-mannose inhibition, anti-CD66b mAb inhibition of cytolysis, flow cytometry","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct imaging of CD11b redistribution plus functional cytolysis inhibition; single lab","pmids":["10233903"],"is_preprint":false},{"year":2014,"finding":"Soluble CEACAM8-Fc binds to CEACAM1 expressed on human airway epithelium. This interaction reduces TLR2-dependent inflammatory responses and is accompanied by tyrosine phosphorylation of the ITIM of CEACAM1 and recruitment of the phosphatase SHP-1, which negatively regulates TLR2-dependent PI3K-Akt activation. Granulocytes release CEACAM8 in response to bacterial DNA in a TLR9-dependent manner.","method":"Recombinant CEACAM8-Fc binding assay, CEACAM1-positive epithelial cell stimulation, ITIM phosphorylation assay, SHP-1 co-immunoprecipitation, PI3K-Akt pathway measurement, TLR9 dependency assay","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (recombinant protein binding, phosphorylation, phosphatase recruitment, signaling pathway inhibition) establishing a mechanistic pathway in a single study","pmids":["24743304"],"is_preprint":false},{"year":2019,"finding":"Extracellular chromatin (including mononucleosomes and long chromatin fragments) triggers secretion of soluble CEACAM8 by primary human PMN in a time- and concentration-dependent manner; secretion involves both neo-synthesis of soluble CEACAM8 and release through degranulation.","method":"Primary human PMN stimulation with extracellular chromatin/nucleosomes, CEACAM8 ELISA in supernatant, degranulation assay, protein synthesis inhibition","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two mechanisms distinguished (neo-synthesis vs. degranulation) using complementary assays; single lab","pmids":["31258530"],"is_preprint":false},{"year":1998,"finding":"The CGM6 gene (encoding CD66b/NCA-95) contains all regulatory elements necessary for granulocyte-specific expression within a 16.5 kb cosmid spanning six exons; transgenic mice expressing this cosmid show CD66b exclusively on granulocytes, first appearing in fetal liver at day 12.5 and bone marrow at day 17.5.","method":"Transgenic mouse generation with cosmid insert, Northern blot, immunohistochemistry, FACScan analysis of bone marrow and spleen","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vivo transgenic model with multiple validation methods establishing complete gene regulation and cell-type specificity","pmids":["9427723"],"is_preprint":false}],"current_model":"CEACAM8 (CD66b) is a GPI-anchored, highly glycosylated granulocyte surface glycoprotein stored in specific and gelatinase granules that, upon activation, translocates to the cell surface where it localizes in lipid rafts and constitutively associates with the β2 integrin CD11b; its N-terminal domain mediates heterophilic adhesion to CEACAM6, while ligand engagement (galectin-3 or cross-linking antibody) activates Src-family kinase Hck, induces CD11b clustering, and triggers superoxide production, degranulation, and pre-stored IL-8 release; in its soluble secreted form (released by granulocytes in response to bacterial DNA via TLR9 or extracellular chromatin), CEACAM8 binds CEACAM1 on airway epithelium, phosphorylates its ITIM, recruits SHP-1, and suppresses TLR2-driven PI3K-Akt signaling, thereby acting as a negative regulator of airway inflammation."},"narrative":{"mechanistic_narrative":"CEACAM8 (CD66b/CGM6/NCA-95) is a GPI-anchored, granulocyte-specific glycoprotein that functions both as a surface activation receptor on neutrophils and eosinophils and as a secreted negative regulator of mucosal inflammation [PMID:1370882, PMID:18056392, PMID:24743304]. It is a ~100 kDa glycoprotein released by PI-PLC, stored in gelatinase and specific granules of resting cells, and mobilized to the surface upon activation, where its expression is tightly restricted to the granulocyte lineage [PMID:1370882, PMID:10553088, PMID:9427723]. Its N-terminal domain mediates carbohydrate-independent heterophilic adhesion to CEACAM6, through residues mapped by mutagenesis that overlap the CEACAM6 homophilic and Neisseria Opa binding sites [PMID:8645267, PMID:11590190]. At the cell surface CEACAM8 resides in lipid rafts and constitutively associates with the β2 integrin CD11b; engagement by cross-linking antibody or its natural ligand galectin-3 activates the Src-family kinase Hck, drives D-mannose-sensitive clustering of CD11b, upregulates CD11/CD18, and triggers calcium-dependent adhesion, superoxide production, degranulation, and release of pre-stored IL-8 [PMID:8699114, PMID:10553088, PMID:18056392, PMID:17002897, PMID:10233903]. In its soluble secreted form—released by granulocytes in response to bacterial DNA via TLR9 and to extracellular chromatin—CEACAM8 binds CEACAM1 on airway epithelium, inducing ITIM phosphorylation, SHP-1 recruitment, and suppression of TLR2-driven PI3K-Akt signaling [PMID:24743304, PMID:31258530].","teleology":[{"year":1992,"claim":"Establishing that CD66b is a GPI-anchored granulocyte surface glycoprotein defined the molecular nature of the protein and explained how it could be mobilized and shed.","evidence":"Immunoprecipitation, PI-PLC cleavage, and deglycosylation of granulocyte surface protein","pmids":["1370882"],"confidence":"High","gaps":["Did not define signaling or adhesion function","No structural detail on the glycosylated ectodomain"]},{"year":1996,"claim":"Demonstrating that antibody engagement of CD66b triggers calcium-dependent upregulation of CD11/CD18 and increased neutrophil adhesion showed the molecule transmits activating signals rather than acting as a passive marker.","evidence":"Functional adhesion assay, calcium chelation, and sequential desensitization with CD66 mAbs","pmids":["8699114"],"confidence":"Medium","gaps":["Identity of the physiological ligand unknown at this stage","Downstream kinases not defined"]},{"year":1996,"claim":"Reconstituting heterophilic adhesion with recombinant proteins established that CD66b binds CD66c (NCA) through N-terminal domains independently of carbohydrate, linking adhesion to functional superoxide output.","evidence":"Soluble recombinant protein binding, deglycosylation control, CHO transfectant adhesion, superoxide assay","pmids":["8645267"],"confidence":"High","gaps":["Residues mediating adhesion not yet mapped","In vivo relevance of heterophilic adhesion untested"]},{"year":1998,"claim":"Transgenic expression of a CGM6 cosmid showed the gene carries all elements for granulocyte-restricted expression, defining its lineage specificity and developmental onset.","evidence":"Transgenic mice with cosmid insert, Northern blot, immunohistochemistry, FACS of bone marrow/spleen","pmids":["9427723"],"confidence":"High","gaps":["No loss-of-function phenotype examined","Regulatory elements not individually mapped"]},{"year":1999,"claim":"Identifying CD66b as a major neutrophil galectin-3 receptor stored in granules connected the molecule to an endogenous lectin ligand and to regulated mobilization.","evidence":"Galectin-3-Sepharose affinity chromatography, subcellular granule fractionation, immunoblot, HL-60 differentiation","pmids":["10553088"],"confidence":"High","gaps":["Functional consequence of galectin-3 binding not resolved here","Binding stoichiometry/affinity not quantified"]},{"year":1999,"claim":"Showing lectin-like physical interaction with CD11b/CD18 and D-mannose-sensitive CD11b clustering, plus a requirement in antibody-dependent cytolysis, positioned CD66b as a functional partner of β2 integrins.","evidence":"Immunofluorescence redistribution, D-mannose inhibition, anti-CD66b mAb inhibition of cytolysis","pmids":["10233903"],"confidence":"Medium","gaps":["Molecular basis of the lectin-like interaction undefined","Signaling intermediates not identified"]},{"year":2001,"claim":"Mapping critical N-domain residues for CEACAM8–CEACAM6 heterophilic adhesion refined the binding interface and distinguished it from homophilic and pathogen-binding sites.","evidence":"Homologue-scanning mutagenesis, chimeric protein expression, CHO transfectant adhesion assay","pmids":["11590190"],"confidence":"High","gaps":["No co-crystal structure of the interface","Physiological context of the adhesion not addressed"]},{"year":2006,"claim":"Demonstrating that CD66b cross-linking releases pre-stored IL-8 without de novo synthesis distinguished its rapid-release signaling output from transcription-dependent cytokine responses.","evidence":"CD66b mAb cross-linking, IL-8 ELISA, comparison to LPS-driven synthesis","pmids":["17002897"],"confidence":"Medium","gaps":["Storage compartment for IL-8 not defined","Signaling pathway from CD66b to release not mapped"]},{"year":2007,"claim":"Assembling the surface signaling mechanism—lipid raft localization, constitutive CD11b association, galectin-3/mAb engagement activating Hck, and GPI/raft-dependent effector functions—integrated CD66b into a defined raft-based activation module on eosinophils.","evidence":"Co-IP, lipid raft fractionation, GPI removal, mAb cross-linking, superoxide and degranulation assays, confocal microscopy","pmids":["18056392"],"confidence":"High","gaps":["How a GPI-anchored protein transmits signal across the membrane mechanistically unresolved","Relative roles of Hck versus other kinases unquantified"]},{"year":2014,"claim":"Showing that soluble CEACAM8 binds epithelial CEACAM1 to drive ITIM phosphorylation, SHP-1 recruitment, and suppression of TLR2 PI3K-Akt signaling revealed an anti-inflammatory secreted function distinct from its surface activating role.","evidence":"Recombinant CEACAM8-Fc binding, ITIM phosphorylation, SHP-1 co-IP, PI3K-Akt readout, TLR9 dependency","pmids":["24743304"],"confidence":"High","gaps":["In vivo demonstration of airway inflammation suppression not shown","Affinity of soluble CEACAM8 for CEACAM1 not quantified"]},{"year":2019,"claim":"Identifying extracellular chromatin as a trigger for soluble CEACAM8 secretion via both neo-synthesis and degranulation clarified the stimulus and routes generating the anti-inflammatory soluble form.","evidence":"Primary PMN stimulation with chromatin/nucleosomes, CEACAM8 ELISA, degranulation and protein synthesis inhibition assays","pmids":["31258530"],"confidence":"Medium","gaps":["Receptor sensing extracellular chromatin not defined","Relative contribution of synthesis versus degranulation in vivo unknown"]},{"year":null,"claim":"How CEACAM8's two functional modes—surface raft-based activation of granulocytes versus secreted CEACAM1-mediated immunosuppression—are coordinated in vivo, and the precise transmembrane signaling mechanism for a GPI-anchored receptor, remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of CEACAM8 ectodomain or its complexes","Balance of activating versus suppressive functions during infection untested in vivo","Transmembrane signal transduction mechanism unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[2,4]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,5]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[8]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,5]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[3]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[8,9]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[5,8]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,8]}],"complexes":[],"partners":["CEACAM6","ITGAM","CEACAM1","LGALS3","HCK","PTPN6"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P31997","full_name":"Cell adhesion molecule CEACAM8","aliases":["CD67 antigen","Carcinoembryonic antigen CGM6","Carcinoembryonic antigen-related cell adhesion molecule 8","CEA cell adhesion molecule 8","Non-specific cross-reacting antigen NCA-95"],"length_aa":349,"mass_kda":38.2,"function":"Cell surface glycoprotein that plays a role in cell adhesion in a calcium-independent manner (PubMed:11590190, PubMed:2022629, PubMed:8776764). Mediates heterophilic cell adhesion with other carcinoembryonic antigen-related cell adhesion molecules, such as CEACAM6 (PubMed:11590190, PubMed:2022629, PubMed:8776764). Heterophilic interaction with CEACAM8 occurs in activated neutrophils (PubMed:8776764)","subcellular_location":"Cell membrane; Cell surface","url":"https://www.uniprot.org/uniprotkb/P31997/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CEACAM8","classification":"Not Classified","n_dependent_lines":5,"n_total_lines":1208,"dependency_fraction":0.0041390728476821195},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CEACAM8","total_profiled":1310},"omim":[{"mim_id":"615747","title":"CEA CELL ADHESION MOLECULE 8; CEACAM8","url":"https://www.omim.org/entry/615747"},{"mim_id":"163980","title":"CEA CELL ADHESION MOLECULE 6; CEACAM6","url":"https://www.omim.org/entry/163980"},{"mim_id":"114890","title":"CEA CELL ADHESION MOLECULE 5; CEACAM5","url":"https://www.omim.org/entry/114890"},{"mim_id":"109770","title":"CEA CELL ADHESION MOLECULE 1; CEACAM1","url":"https://www.omim.org/entry/109770"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"bone marrow","ntpm":204.8}],"url":"https://www.proteinatlas.org/search/CEACAM8"},"hgnc":{"alias_symbol":["CD66b"],"prev_symbol":["CGM6"]},"alphafold":{"accession":"P31997","domains":[{"cath_id":"2.60.40.10","chopping":"38-142","consensus_level":"high","plddt":97.0019,"start":38,"end":142},{"cath_id":"2.60.40.10","chopping":"149-226","consensus_level":"high","plddt":95.5772,"start":149,"end":226},{"cath_id":"2.60.40.10","chopping":"242-320","consensus_level":"high","plddt":96.5025,"start":242,"end":320}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P31997","model_url":"https://alphafold.ebi.ac.uk/files/AF-P31997-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P31997-F1-predicted_aligned_error_v6.png","plddt_mean":86.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CEACAM8","jax_strain_url":"https://www.jax.org/strain/search?query=CEACAM8"},"sequence":{"accession":"P31997","fasta_url":"https://rest.uniprot.org/uniprotkb/P31997.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P31997/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P31997"}},"corpus_meta":[{"pmid":"21953630","id":"PMC_21953630","title":"Predictive clinical outcome of the intratumoral CD66b-positive neutrophil-to-CD8-positive T-cell ratio in patients with resectable nonsmall cell lung cancer.","date":"2011","source":"Cancer","url":"https://pubmed.ncbi.nlm.nih.gov/21953630","citation_count":147,"is_preprint":false},{"pmid":"8699114","id":"PMC_8699114","title":"CD66a, CD66b, CD66c, and CD66d each independently stimulate neutrophils.","date":"1996","source":"Journal of leukocyte biology","url":"https://pubmed.ncbi.nlm.nih.gov/8699114","citation_count":120,"is_preprint":false},{"pmid":"18056392","id":"PMC_18056392","title":"CD66b regulates adhesion and activation of human eosinophils.","date":"2007","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/18056392","citation_count":96,"is_preprint":false},{"pmid":"10553088","id":"PMC_10553088","title":"Identification of CD66a and CD66b as the major galectin-3 receptor candidates in human neutrophils.","date":"1999","source":"Journal of 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triggers a transient calcium-dependent activation signal that upregulates CD11/CD18 on the neutrophil surface and increases neutrophil adhesion to HUVEC monolayers; this response requires physiological extracellular calcium at or near the time of antibody binding, and CD66b can independently transmit signals in neutrophils as shown by sequential desensitization experiments.\",\n      \"method\": \"Functional adhesion assay with CD66 mAbs, calcium chelation experiments, sequential desensitization, flow cytometry\",\n      \"journal\": \"Journal of leukocyte biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal functional assays (adhesion, desensitization, calcium requirement) in single lab\",\n      \"pmids\": [\"8699114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"CD66b (CGM6/NCA-95) is a GPI-anchored glycoprotein of ~100 kDa on granulocyte surfaces; it can be released by phosphatidylinositol-specific phospholipase C, and its deglycosylated core is ~38 kDa, consistent with the CGM6-encoded protein.\",\n      \"method\": \"Immunoprecipitation, SDS-PAGE, PI-PLC cleavage, immunoblotting with anti-CD67 and anti-NCA antibodies\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct biochemical demonstration of GPI anchor (PI-PLC release), molecular weight characterization, and antibody cross-reactivity with recombinant CGM6 protein\",\n      \"pmids\": [\"1370882\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"CD66b (CGM6) mediates heterophilic cell adhesion with CD66c (NCA); this interaction occurs via the N-terminal domains of both molecules and does not require the carbohydrate portions, as deglycosylated recombinant proteins retain adhesion activity. Activated neutrophils adhere to immobilized CD66b, and this adhesion induces superoxide anion release.\",\n      \"method\": \"Soluble recombinant protein binding assay, deglycosylation, CHO transfectant adhesion, N-domain antibody inhibition, superoxide anion assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted adhesion with recombinant proteins, deglycosylation control, domain-blocking antibodies, and functional superoxide readout in single study\",\n      \"pmids\": [\"8645267\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"CD66b is stored in gelatinase and specific granules of resting neutrophils and mobilized to the cell surface upon activation; it was identified as one of two major galectin-3 receptors on neutrophils (alongside CD66a) by galectin-3-Sepharose affinity chromatography of granule contents, with the ~100 kDa eluted band confirmed as CD66b by immunoblotting.\",\n      \"method\": \"Galectin-3-Sepharose affinity chromatography, SDS-PAGE, immunoblotting, subcellular fractionation of neutrophil granules, HL-60 differentiation model\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct biochemical purification from native granule fractions, immunoblot confirmation, functional validation using HL-60 cells lacking specific/gelatinase granules\",\n      \"pmids\": [\"10553088\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The N-terminal domain (N-domain) of CEACAM8 (CD66b) mediates heterophilic adhesion to CEACAM6 (CD66c). By homologue-scanning mutagenesis of CHO transfectants expressing chimeric/mutant proteins, critical residues for CEACAM6–CEACAM8 heterophilic adhesion were mapped; these overlap with, but are not identical to, residues required for CEACAM6 homophilic adhesion and Neisseria Opa protein binding.\",\n      \"method\": \"CHO transfectant adhesion assay, homologue-scanning mutagenesis, chimeric protein expression\",\n      \"journal\": \"Journal of leukocyte biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — systematic mutagenesis with functional readout in reconstituted cell-adhesion system\",\n      \"pmids\": [\"11590190\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"CD66b (CEACAM8) on human eosinophils is localized in lipid rafts and is constitutively and physically associated with the β2 integrin CD11b. Engagement of CD66b by mAb or its natural ligand galectin-3 activates the Src-family kinase Hck and induces cellular adhesion, superoxide production, and degranulation. Cross-linking of CD66b causes striking clustering of CD11b. Disruption of lipid rafts or removal of the GPI anchor inhibits these responses.\",\n      \"method\": \"Co-immunoprecipitation, lipid raft fractionation, GPI anchor removal, mAb cross-linking, superoxide assay, degranulation assay, confocal microscopy\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (co-IP, raft disruption, GPI removal, functional assays) in a single study establishing mechanism\",\n      \"pmids\": [\"18056392\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Cross-linking of CD66b on peripheral blood neutrophils induces release of pre-stored interleukin-8 (IL-8) from intracellular storage without de novo synthesis, in contrast to LPS stimulation which drives de novo cytokine synthesis.\",\n      \"method\": \"CD66b cross-linking with mAb, ELISA for IL-8, comparison with LPS-stimulated de novo synthesis\",\n      \"journal\": \"Human immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional assay with cross-linking and comparison condition; single lab, two orthogonal methods (ELISA + cross-linking)\",\n      \"pmids\": [\"17002897\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"CD66b (GPI-anchored) and CD11b/CD18 undergo lectin-like physical interactions on the neutrophil surface; cross-linking of CD66b redistributes CD11b into discrete clusters via a D-mannose-sensitive process. CD66b is required for neutrophil cytolytic activity in GM-CSF/Lym-1-mediated antibody-dependent cytolysis, as shown by inhibitory anti-CD66b mAb.\",\n      \"method\": \"Immunofluorescence redistribution assay, D-mannose inhibition, anti-CD66b mAb inhibition of cytolysis, flow cytometry\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct imaging of CD11b redistribution plus functional cytolysis inhibition; single lab\",\n      \"pmids\": [\"10233903\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Soluble CEACAM8-Fc binds to CEACAM1 expressed on human airway epithelium. This interaction reduces TLR2-dependent inflammatory responses and is accompanied by tyrosine phosphorylation of the ITIM of CEACAM1 and recruitment of the phosphatase SHP-1, which negatively regulates TLR2-dependent PI3K-Akt activation. Granulocytes release CEACAM8 in response to bacterial DNA in a TLR9-dependent manner.\",\n      \"method\": \"Recombinant CEACAM8-Fc binding assay, CEACAM1-positive epithelial cell stimulation, ITIM phosphorylation assay, SHP-1 co-immunoprecipitation, PI3K-Akt pathway measurement, TLR9 dependency assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (recombinant protein binding, phosphorylation, phosphatase recruitment, signaling pathway inhibition) establishing a mechanistic pathway in a single study\",\n      \"pmids\": [\"24743304\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Extracellular chromatin (including mononucleosomes and long chromatin fragments) triggers secretion of soluble CEACAM8 by primary human PMN in a time- and concentration-dependent manner; secretion involves both neo-synthesis of soluble CEACAM8 and release through degranulation.\",\n      \"method\": \"Primary human PMN stimulation with extracellular chromatin/nucleosomes, CEACAM8 ELISA in supernatant, degranulation assay, protein synthesis inhibition\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two mechanisms distinguished (neo-synthesis vs. degranulation) using complementary assays; single lab\",\n      \"pmids\": [\"31258530\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"The CGM6 gene (encoding CD66b/NCA-95) contains all regulatory elements necessary for granulocyte-specific expression within a 16.5 kb cosmid spanning six exons; transgenic mice expressing this cosmid show CD66b exclusively on granulocytes, first appearing in fetal liver at day 12.5 and bone marrow at day 17.5.\",\n      \"method\": \"Transgenic mouse generation with cosmid insert, Northern blot, immunohistochemistry, FACScan analysis of bone marrow and spleen\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vivo transgenic model with multiple validation methods establishing complete gene regulation and cell-type specificity\",\n      \"pmids\": [\"9427723\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CEACAM8 (CD66b) is a GPI-anchored, highly glycosylated granulocyte surface glycoprotein stored in specific and gelatinase granules that, upon activation, translocates to the cell surface where it localizes in lipid rafts and constitutively associates with the β2 integrin CD11b; its N-terminal domain mediates heterophilic adhesion to CEACAM6, while ligand engagement (galectin-3 or cross-linking antibody) activates Src-family kinase Hck, induces CD11b clustering, and triggers superoxide production, degranulation, and pre-stored IL-8 release; in its soluble secreted form (released by granulocytes in response to bacterial DNA via TLR9 or extracellular chromatin), CEACAM8 binds CEACAM1 on airway epithelium, phosphorylates its ITIM, recruits SHP-1, and suppresses TLR2-driven PI3K-Akt signaling, thereby acting as a negative regulator of airway inflammation.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CEACAM8 (CD66b/CGM6/NCA-95) is a GPI-anchored, granulocyte-specific glycoprotein that functions both as a surface activation receptor on neutrophils and eosinophils and as a secreted negative regulator of mucosal inflammation [#1, #5, #8]. It is a ~100 kDa glycoprotein released by PI-PLC, stored in gelatinase and specific granules of resting cells, and mobilized to the surface upon activation, where its expression is tightly restricted to the granulocyte lineage [#1, #3, #10]. Its N-terminal domain mediates carbohydrate-independent heterophilic adhesion to CEACAM6, through residues mapped by mutagenesis that overlap the CEACAM6 homophilic and Neisseria Opa binding sites [#2, #4]. At the cell surface CEACAM8 resides in lipid rafts and constitutively associates with the \\u03b22 integrin CD11b; engagement by cross-linking antibody or its natural ligand galectin-3 activates the Src-family kinase Hck, drives D-mannose-sensitive clustering of CD11b, upregulates CD11/CD18, and triggers calcium-dependent adhesion, superoxide production, degranulation, and release of pre-stored IL-8 [#0, #3, #5, #6, #7]. In its soluble secreted form\\u2014released by granulocytes in response to bacterial DNA via TLR9 and to extracellular chromatin\\u2014CEACAM8 binds CEACAM1 on airway epithelium, inducing ITIM phosphorylation, SHP-1 recruitment, and suppression of TLR2-driven PI3K-Akt signaling [#8, #9].\",\n  \"teleology\": [\n    {\n      \"year\": 1992,\n      \"claim\": \"Establishing that CD66b is a GPI-anchored granulocyte surface glycoprotein defined the molecular nature of the protein and explained how it could be mobilized and shed.\",\n      \"evidence\": \"Immunoprecipitation, PI-PLC cleavage, and deglycosylation of granulocyte surface protein\",\n      \"pmids\": [\"1370882\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define signaling or adhesion function\", \"No structural detail on the glycosylated ectodomain\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Demonstrating that antibody engagement of CD66b triggers calcium-dependent upregulation of CD11/CD18 and increased neutrophil adhesion showed the molecule transmits activating signals rather than acting as a passive marker.\",\n      \"evidence\": \"Functional adhesion assay, calcium chelation, and sequential desensitization with CD66 mAbs\",\n      \"pmids\": [\"8699114\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity of the physiological ligand unknown at this stage\", \"Downstream kinases not defined\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Reconstituting heterophilic adhesion with recombinant proteins established that CD66b binds CD66c (NCA) through N-terminal domains independently of carbohydrate, linking adhesion to functional superoxide output.\",\n      \"evidence\": \"Soluble recombinant protein binding, deglycosylation control, CHO transfectant adhesion, superoxide assay\",\n      \"pmids\": [\"8645267\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Residues mediating adhesion not yet mapped\", \"In vivo relevance of heterophilic adhesion untested\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Transgenic expression of a CGM6 cosmid showed the gene carries all elements for granulocyte-restricted expression, defining its lineage specificity and developmental onset.\",\n      \"evidence\": \"Transgenic mice with cosmid insert, Northern blot, immunohistochemistry, FACS of bone marrow/spleen\",\n      \"pmids\": [\"9427723\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No loss-of-function phenotype examined\", \"Regulatory elements not individually mapped\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Identifying CD66b as a major neutrophil galectin-3 receptor stored in granules connected the molecule to an endogenous lectin ligand and to regulated mobilization.\",\n      \"evidence\": \"Galectin-3-Sepharose affinity chromatography, subcellular granule fractionation, immunoblot, HL-60 differentiation\",\n      \"pmids\": [\"10553088\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of galectin-3 binding not resolved here\", \"Binding stoichiometry/affinity not quantified\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Showing lectin-like physical interaction with CD11b/CD18 and D-mannose-sensitive CD11b clustering, plus a requirement in antibody-dependent cytolysis, positioned CD66b as a functional partner of \\u03b22 integrins.\",\n      \"evidence\": \"Immunofluorescence redistribution, D-mannose inhibition, anti-CD66b mAb inhibition of cytolysis\",\n      \"pmids\": [\"10233903\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of the lectin-like interaction undefined\", \"Signaling intermediates not identified\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Mapping critical N-domain residues for CEACAM8\\u2013CEACAM6 heterophilic adhesion refined the binding interface and distinguished it from homophilic and pathogen-binding sites.\",\n      \"evidence\": \"Homologue-scanning mutagenesis, chimeric protein expression, CHO transfectant adhesion assay\",\n      \"pmids\": [\"11590190\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No co-crystal structure of the interface\", \"Physiological context of the adhesion not addressed\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrating that CD66b cross-linking releases pre-stored IL-8 without de novo synthesis distinguished its rapid-release signaling output from transcription-dependent cytokine responses.\",\n      \"evidence\": \"CD66b mAb cross-linking, IL-8 ELISA, comparison to LPS-driven synthesis\",\n      \"pmids\": [\"17002897\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Storage compartment for IL-8 not defined\", \"Signaling pathway from CD66b to release not mapped\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Assembling the surface signaling mechanism\\u2014lipid raft localization, constitutive CD11b association, galectin-3/mAb engagement activating Hck, and GPI/raft-dependent effector functions\\u2014integrated CD66b into a defined raft-based activation module on eosinophils.\",\n      \"evidence\": \"Co-IP, lipid raft fractionation, GPI removal, mAb cross-linking, superoxide and degranulation assays, confocal microscopy\",\n      \"pmids\": [\"18056392\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How a GPI-anchored protein transmits signal across the membrane mechanistically unresolved\", \"Relative roles of Hck versus other kinases unquantified\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showing that soluble CEACAM8 binds epithelial CEACAM1 to drive ITIM phosphorylation, SHP-1 recruitment, and suppression of TLR2 PI3K-Akt signaling revealed an anti-inflammatory secreted function distinct from its surface activating role.\",\n      \"evidence\": \"Recombinant CEACAM8-Fc binding, ITIM phosphorylation, SHP-1 co-IP, PI3K-Akt readout, TLR9 dependency\",\n      \"pmids\": [\"24743304\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo demonstration of airway inflammation suppression not shown\", \"Affinity of soluble CEACAM8 for CEACAM1 not quantified\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identifying extracellular chromatin as a trigger for soluble CEACAM8 secretion via both neo-synthesis and degranulation clarified the stimulus and routes generating the anti-inflammatory soluble form.\",\n      \"evidence\": \"Primary PMN stimulation with chromatin/nucleosomes, CEACAM8 ELISA, degranulation and protein synthesis inhibition assays\",\n      \"pmids\": [\"31258530\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor sensing extracellular chromatin not defined\", \"Relative contribution of synthesis versus degranulation in vivo unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How CEACAM8's two functional modes\\u2014surface raft-based activation of granulocytes versus secreted CEACAM1-mediated immunosuppression\\u2014are coordinated in vivo, and the precise transmembrane signaling mechanism for a GPI-anchored receptor, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model of CEACAM8 ectodomain or its complexes\", \"Balance of activating versus suppressive functions during infection untested in vivo\", \"Transmembrane signal transduction mechanism unresolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [2, 4]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [8]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 5]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [8, 9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [5, 8]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 8]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CEACAM6\", \"ITGAM\", \"CEACAM1\", \"LGALS3\", \"HCK\", \"PTPN6\"],\n    \"other_free_text\": []\n  }\n}\n```","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}