{"gene":"ICAM2","run_date":"2026-04-28T18:06:53","timeline":{"discoveries":[{"year":1989,"finding":"ICAM-2 was identified as a second ligand for the leukocyte integrin LFA-1 (CD11a/CD18). ICAM-2 is an integral membrane protein with two immunoglobulin-like domains, most closely related to the two N-terminal domains of ICAM-1 (34% identity), and supports LFA-1-dependent cell adhesion.","method":"Functional cloning using a novel ligand identification method; transfection of COS cells with ICAM-2 cDNA and cell adhesion assays","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 — original functional cloning with cell adhesion assays, highly cited foundational paper","pmids":["2497351"],"is_preprint":false},{"year":1991,"finding":"ICAM-2 binds LFA-1; monoclonal antibody CBR-IC2/2 totally inhibits ICAM-2+ cell binding to purified LFA-1. ICAM-2 accounts for LFA-1-dependent adhesion to both stimulated and unstimulated endothelium together with ICAM-1. ICAM-2 has a peptide backbone of ~31 kDa (Mr ~60,000 as a broad glycosylated band), and is constitutively expressed on endothelium and hematopoietic cells with little inflammatory induction.","method":"Monoclonal antibody generation, immunoprecipitation, N-glycanase treatment, cell binding assays to purified LFA-1","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 1-2 — blocking mAb, biochemical characterization, replicated functional adhesion assays","pmids":["1676048"],"is_preprint":false},{"year":1995,"finding":"ICAM-2 (CD102) binds to the leukocyte integrin CD11b/CD18 (Mac-1) through the CD11b A domain, in addition to its known interaction with CD11a/CD18 (LFA-1).","method":"Cell binding assays with purified CD11b/CD18; domain-specific blocking experiments using A-domain constructs","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — direct binding demonstrated with purified protein and domain-level mapping","pmids":["7561061"],"is_preprint":false},{"year":1997,"finding":"Crystal structure of ICAM-2 extracellular region was solved. Glu-37 is critical for LFA-1 binding and is proposed to coordinate Mg2+ in the LFA-1 I domain. The LFA-1 recognition surface is relatively flat, lying on the GFC beta-sheet of domain 1, contrasting with loop-presented acidic residues in non-I-domain integrin ligands. A bend between domains 1 and 2 and N-linked glycan tripod arrangement may orient the recognition surface.","method":"X-ray crystallography of ICAM-2 extracellular domain","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with functional interpretation; independently validated by mutagenesis in subsequent work","pmids":["9153399"],"is_preprint":false},{"year":1999,"finding":"Mutagenesis of ICAM-2 based on its crystal structure mapped the LFA-1 binding site to a diagonal ridge across the GFC beta-sheet including the CD edge of domain 1. Glu-37 ligates the Mg2+ in the LFA-1 I domain. The site is oblong and confined to the upper part of domain 1, distinct from the VCAM-1 binding surface for alpha4 integrins.","method":"Site-directed mutagenesis of ICAM-2 combined with cell adhesion assays and structural interpretation","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis validated crystal structure, multiple mutants tested","pmids":["10077629"],"is_preprint":false},{"year":1996,"finding":"ICAM-2 binds alpha-actinin through its cytoplasmic domain (residues 231-254, with optimal binding at amino acids 241-248). Alpha-actinin colocalized with ICAM-2 in endothelial cells. Multiple regions of alpha-actinin can mediate this interaction.","method":"Affinity pulldown using ICAM-2 cytoplasmic peptide as matrix from placental lysates, immunoblotting, 125I-labeled alpha-actinin binding, confocal microscopy colocalization, overlapping octapeptide competition, bacterially expressed alpha-actinin domain fusion proteins","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro reconstitution with purified proteins, domain mapping, colocalization; multiple orthogonal methods","pmids":["8824270"],"is_preprint":false},{"year":1998,"finding":"ERM proteins (ezrin/radixin/moesin) bind directly to a positively charged amino acid cluster in the juxta-membrane cytoplasmic domain of ICAM-2 (28 amino acids). This binding concentrates ICAM-2 at microvilli. Site-directed mutagenesis of these clusters abolishes ERM binding.","method":"GST fusion protein pulldown (in vitro binding), immunoprecipitation, chimeric E-cadherin construct expression in L fibroblasts, site-directed mutagenesis, colocalization by microscopy","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods including mutagenesis and reconstitution in cells","pmids":["9472040"],"is_preprint":false},{"year":1998,"finding":"Ezrin interacts directly with ICAM-2 cytoplasmic tail with a KD of 3.3×10^-7 M. ICAM-2 colocalizes with ezrin in microvillar projections in transfected cells. Phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) enhances the ezrin–ICAM-2 interaction and binds to the ICAM-2 cytoplasmic tail, identifying ICAM-2 as the first adhesion protein shown to interact with PtdIns(4,5)P2.","method":"Affinity precipitation, microtiter binding assay, co-immunoprecipitation, surface plasmon resonance, PtdIns(4,5)P2 binding assays, confocal colocalization in transfected cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — SPR gives quantitative KD, multiple orthogonal methods, novel biochemical finding replicated across methods","pmids":["9705328"],"is_preprint":false},{"year":1996,"finding":"ICAM-2 redistribution to uropods (bud-like projections) by ezrin confers NK cell sensitivity to target cells. Ezrin transfection into NK-resistant cells induces uropod formation, redistributes ICAM-2 from uniform surface distribution to concentrated uropods, and sensitizes targets to IL-2-activated NK killing.","method":"Transfection of ezrin into NK-resistant cells, fluorescence imaging of ICAM-2/ezrin localization, NK cytotoxicity assays","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 — direct functional consequence of localization change demonstrated by transfection and cytotoxicity assay; published in Nature","pmids":["8717043"],"is_preprint":false},{"year":2002,"finding":"ICAM-2 activates the PI3K/AKT pathway. ICAM-2 induces tyrosine phosphorylation of ezrin and PI3K membrane translocation, leading to PtdIns(3,4,5)P3 production, PDK-1 and AKT activation, and phosphorylation of AKT substrates BAD, GSK3, and FKHR. ICAM-2 clustering protects primary human CD19+ B cells from TNFα- and Fas-mediated apoptosis. ICAM-2 engagement by LFA-1 on CD4+ T cells induces AKT activity in CD19+ cells in the absence of MHC-peptide interaction.","method":"Genetic screen, reporter assays, biochemical signaling assays (phosphorylation of ezrin, AKT, BAD, GSK3, FKHR), single-cell analysis of apoptosis, ICAM-2 clustering experiments","journal":"Immunity","confidence":"High","confidence_rationale":"Tier 2 — multiple downstream signaling nodes measured, mechanistic pathway mapped, functional apoptosis protection demonstrated","pmids":["11825565"],"is_preprint":false},{"year":2002,"finding":"ICAM-1 cross-linking activates RhoA and induces stress fiber formation in endothelial cells, and stimulates c-fos and rhoA transcription, while ICAM-2 cross-linking does not activate RhoA or alter actin organization, demonstrating distinct downstream signaling despite both colocalizing with moesin in microvilli.","method":"Antibody cross-linking of ICAM-1 and ICAM-2 in HUVECs, RhoA activity assay, confocal microscopy, reporter gene assays for c-fos and rhoA transcription","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — direct comparison with functional GTPase assays and transcriptional reporters, multiple methods","pmids":["12097408"],"is_preprint":false},{"year":2005,"finding":"Endothelial ICAM-2 mediates angiogenesis. ICAM-2-deficient mice and cells show impaired angiogenesis in vitro and in vivo. ICAM-2 supports homophilic interaction involved in tube formation. ICAM-2-deficient cells show defective migration and increased apoptosis. ICAM-2 activates the small GTPase Rac, required for tube formation and migration.","method":"ICAM-2-deficient mice and endothelial cells, in vitro tube formation and migration assays, in vivo angiogenesis models, Rac GTPase activity assays, apoptosis assays","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with multiple phenotypic readouts, GTPase assay, in vitro and in vivo validation","pmids":["15920013"],"is_preprint":false},{"year":1993,"finding":"A synthetic peptide from ICAM-2 spanning residues 21-42 of the first immunoglobulin domain binds specifically to purified CD11a/CD18 (LFA-1), inhibits adhesion of endothelial cells to LFA-1, and inhibits B lymphoblastoid cell binding to endothelial cells. Leukocytes bind this peptide when coated on plastic.","method":"Synthetic peptide binding assay to purified CD11a/CD18, cell adhesion inhibition assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — direct binding to purified integrin, functional inhibition demonstrated","pmids":["8349630"],"is_preprint":false},{"year":1995,"finding":"An ICAM-2 peptide (residues 21-42) activates NK cell migration by 215% via CD11a/CD18 (LFA-1) ligation, induces F-actin polymerization at the leading edge of migratory NK cells, and increases phosphorylation of 150-kDa and 35-kDa proteins. Ligation of LFA-1 via ICAM-2 peptide transmits signals distinct from antibody cross-linking, triggering locomotion without necessarily triggering cytotoxicity.","method":"Boyden chamber migration assay, anti-CD11a antibody blocking, F-actin staining, phosphotyrosine immunoblotting","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — clean functional assays with inhibitor controls and biochemical readouts from single lab","pmids":["7721764"],"is_preprint":false},{"year":1999,"finding":"ICAM-2 (and a peptide from its LFA-1 binding domain) activates leukocyte adhesion by increasing integrin affinity (inside-out signaling): soluble ICAM-2Fc induces T lymphocyte adhesion to immobilized ICAMs more potently than ICAM-1Fc or ICAM-3Fc, and stimulates binding of soluble recombinant ICAMs to T lymphocytes. The effect requires energy, divalent cations, temperature, and an intact cytoskeleton.","method":"T lymphocyte adhesion assays to immobilized purified ICAMs, flow cytometry for soluble ICAM binding, inhibitor studies (cytoskeletal, kinase inhibitors)","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple assay types, mechanistic inhibitor controls, single lab","pmids":["10352278"],"is_preprint":false},{"year":1998,"finding":"The ICAM-2 promoter is endothelial cell-specific in vitro and in vivo. Critical Sp1 motif at -194 and eight-base pair palindrome at -268 each contribute ~70% of promoter activity. GATA motifs at -145 and -53 each contribute ~61-78%. The Ets family member Erg constitutively binds the ICAM-2 promoter in endothelial cells and transactivates it.","method":"Reporter gene assays, site-directed mutagenesis of promoter elements, gel shift (EMSA) with endothelial nuclear proteins, GATA-2 overexpression transactivation assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — mutagenesis of specific regulatory elements with reporter assays and EMSA validation","pmids":["9565596"],"is_preprint":false},{"year":1999,"finding":"TNF-α and IL-1β down-regulate ICAM-2 expression on endothelium at the transcriptional level by reducing ICAM-2 mRNA to ~40% of control and decreasing ICAM-2 promoter activity. This correlates with loss of ICAM-2 protein from endothelial cell junctions.","method":"Flow cytometry, Northern blotting, ICAM-2 promoter reporter assay in HUVECs, immunocytochemistry","journal":"Cell adhesion and communication","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods (mRNA, protein, promoter activity) from single lab","pmids":["10223354"],"is_preprint":false},{"year":1999,"finding":"TNF-α-mediated down-regulation of ICAM-2 transcription involves three Ets binding sites (EBS) in the promoter. TNF-α decreases binding of nuclear proteins to the -135/-127 EBS. The Ets factor Erg constitutively transactivates the ICAM-2 promoter and is down-regulated by TNF-α, linking Erg to ICAM-2 transcriptional regulation.","method":"Site-directed mutagenesis of promoter Ets sites, EMSA, Erg cDNA transactivation assays in HeLa and HUVEC, Western blot for Erg protein, ex vivo artery model","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1-2 — mutagenesis, EMSA, overexpression transactivation, and ex vivo validation; multiple orthogonal methods","pmids":["10574717"],"is_preprint":false},{"year":2004,"finding":"DC-SIGN binds ICAM-2 via a carbohydrate-dependent interaction. DC-SIGN mediates adhesion and rolling of dendritic cells on primary endothelial cells through the Lewis Y (Le^Y) glycan epitope expressed on ICAM-2. ICAM-2 expressed on CHO cells only serves as a DC-SIGN ligand when properly glycosylated, demonstrating ICAM-2 acts as a scaffold. The Le^Y-presenting enzyme FUT1 directs this endothelial expression; FUT1 silencing reduces DC rolling and adhesion.","method":"Recombinant soluble DC-SIGN binding assays, alanine-scanning mutagenesis of DC-SIGN, CHO cell expression of ICAM-2, FUT1 siRNA knockdown, rolling/adhesion assays under shear flow, glycan chip analysis","journal":"Molecular immunology","confidence":"High","confidence_rationale":"Tier 1-2 — mutagenesis, glycan manipulation, siRNA, functional flow assays; multiple orthogonal methods","pmids":["18155766"],"is_preprint":false},{"year":2004,"finding":"Physiologic sialylation of platelet ICAM-2 (more acidic pI due to N-linked glycosylation) renders it ~50% less able to support LFA-1-dependent T cell adhesion compared to endothelial ICAM-2, and unable to support DC-SIGN-mediated dendritic cell adhesion. Neuraminidase treatment abolishes these functional differences.","method":"Isoelectric focusing of ICAM-2 from platelets vs. HUVECs, N-glycanase and neuraminidase treatment, T cell adhesion assays, DC adhesion assays","journal":"Inflammation","confidence":"Medium","confidence_rationale":"Tier 2 — enzymatic treatments with matched functional adhesion assays, cell-type comparison, single lab","pmids":["15673159"],"is_preprint":false},{"year":2014,"finding":"ICAM-2 regulates endothelial barrier function and vascular permeability through a pathway involving N-cadherin, ERM proteins, and Rac-1 activation. The ERM-binding domain and cytoplasmic tail of ICAM-2 are required for junction formation and contact inhibition. Constitutively active Rac-1 restores barrier function in ICAM-2-deficient cells. In vivo, ICAM-2-deficient mice show increased thrombin-induced vascular permeability.","method":"ICAM-2 siRNA knockdown, ICAM-2-deficient endothelioma lines, re-expression of full-length and mutant ICAM-2 constructs (ΔERM, ΔTAIL), transendothelial electrical resistance measurement, constitutively active Rac-1 rescue, in vivo intravital fluorescence microscopy for albumin extravasation in mouse cremaster","journal":"Cell communication and signaling","confidence":"High","confidence_rationale":"Tier 2 — genetic KO, domain mutants, rescue experiments, in vitro and in vivo validation with multiple readouts","pmids":["24593809"],"is_preprint":false},{"year":1999,"finding":"ICAM-2 deficiency in mice causes prolonged eosinophil accumulation in the lung interstitium during allergic inflammation, delayed transfer to airway lumen, and prolonged airway hyperresponsiveness. This phenotype is caused by lack of ICAM-2 on non-hematopoietic (endothelial) cells, and ICAM-2 deficiency on endothelium directly reduces eosinophil transmigration in vitro. ICAM-2 is also required for normal megakaryocyte progenitor numbers.","method":"ICAM-2-deficient mice (genetic KO), allergic lung inflammation model, histological analysis, bone marrow chimeras to identify non-hematopoietic requirement, in vitro transmigration assays, airway hyperresponsiveness measurement","journal":"Immunity","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with bone marrow chimeras to dissect cell type, in vitro transmigration, multiple phenotypic readouts","pmids":["10023766"],"is_preprint":false},{"year":1998,"finding":"Endothelial ICAM-1 and ICAM-2 are both essential for transendothelial migration of T cells. In ICAM-1-deficient endothelium, only ICAM-2 mediates residual T cell transmigration; PECAM-1, VCAM-1, and E-selectin are not involved in this process.","method":"ICAM-1-deficient endothelioma cells from ICAM-1 mutant mice, retroviral rescue with ICAM-1, antibody blocking of ICAM-2 and other candidates, in vitro transendothelial migration assay","journal":"European journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — genetic KO endothelium with retroviral rescue and antibody blocking; clean epistasis experiment","pmids":["9808177"],"is_preprint":false},{"year":2009,"finding":"Endothelial ICAM-2, JAM-A, and PECAM-1 mediate neutrophil transmigration sequentially. In a stimulus-dependent manner (IL-1β but not TNF-α), when neutrophils lack TNF-α receptor signaling, their transmigration becomes dependent on endothelial ICAM-2, JAM-A, and PECAM-1 acting in sequence, as demonstrated by localization of arrested neutrophils in single KO mice for each molecule.","method":"TNF-receptor-deficient leukocyte transfer into WT and single KO mice (ICAM-2-/-, JAM-A-/-, PECAM-1-/-), fluorescence intravital microscopy, site-of-arrest analysis","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 — in vivo genetic epistasis with multiple KO mice and intravital imaging","pmids":["19211506"],"is_preprint":false},{"year":2010,"finding":"Endothelial ICAM-1 and VCAM-1 mediate shear-resistant T cell arrest, while endothelial ICAM-1 and ICAM-2 (but not VCAM-1) mediate T cell polarization and crawling at the BBB, establishing distinct and sequential roles. Endothelial ICAM-2 specifically contributes to the crawling step required for diapedesis.","method":"Live cell imaging under physiological flow; primary brain microvascular endothelial cells from WT, ICAM-1-deficient, ICAM-2-deficient, and ICAM-1/ICAM-2 double-deficient mice; analysis of T cell arrest, polarization, crawling, and diapedesis","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — live imaging under flow with multiple genetic KO combinations, dissects individual molecular contributions","pmids":["20861356"],"is_preprint":false},{"year":2013,"finding":"Beta-2 integrin-mediated neutrophil crawling on endothelial ICAM-1 and ICAM-2 is a prerequisite for transcellular neutrophil diapedesis across the inflamed BBB. LFA-1 primarily mediates shear-resistant arrest via ICAM-1, while Mac-1 dominates polarization. Both LFA-1 and Mac-1 mediate crawling via ICAM-1 and ICAM-2. Stationary (non-crawling) neutrophils cross exclusively via paracellular route.","method":"Live-cell imaging under flow; WT, CD11a-/-, CD11b-/-, CD18null neutrophils; WT, JAM-A-/-, ICAM-1null, ICAM-2-/-, ICAM-1null/ICAM-2-/- primary mouse BBB endothelial cells","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — comprehensive genetic dissection of integrin/ligand pairs with live imaging, multiple KO combinations","pmids":["24259506"],"is_preprint":false},{"year":2013,"finding":"ICAM-2 is expressed both at EC junctions and on the EC body. Functional or genetic blockade of ICAM-2 reduces neutrophil crawling velocity, increases disrupted stop-start crawling, prolongs neutrophil interaction with EC junctions prior to TEM, and reduces overall extravasation in vivo. Some ICAM-2-dependent functions are mediated through Mac-1.","method":"Real-time in vivo confocal microscopy, ICAM-2-/- mice, functional antibody blockade, Mac-1 pharmacological inhibition, quantitative analysis of crawling parameters","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — in vivo genetic KO with real-time confocal imaging and pharmacological dissection","pmids":["24317296"],"is_preprint":false},{"year":2008,"finding":"ICAM-2 forms a membrane-actin linkage with alpha-actinin and actin in neuroblastoma cells, as demonstrated by co-immunoprecipitation and competitive peptide assays. ICAM-2 expression limits neuroblastoma cell motility, redistributes actin, and suppresses disseminated metastatic tumors in vivo without affecting subcutaneous tumor growth.","method":"Co-immunoprecipitation, competitive peptide assays, in vitro migration assays, in vivo tail vein injection metastasis model, actin redistribution imaging, immunohistochemistry of primary tumors","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — co-IP with competitive peptide confirmation, in vivo model; multiple methods from single lab","pmids":["18978946"],"is_preprint":false},{"year":2014,"finding":"The interaction of ICAM-2 with alpha-actinin via its cytoplasmic domain is critical for ICAM-2-mediated suppression of the metastatic phenotype in neuroblastoma cells in vivo. ICAM-2 variants with mutated alpha-actinin-binding domains fail to completely suppress disseminated tumor development in vivo, despite retaining some inhibitory effects in vitro, indicating both alpha-actinin-dependent and -independent mechanisms.","method":"In silico domain modeling, expression of ICAM-2 alpha-actinin-binding domain mutants, co-precipitation assays, cell adhesion and migration assays, colony formation assays, in vivo tumor dissemination model","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 — domain mutagenesis with in vivo validation; single lab","pmids":["24704826"],"is_preprint":false},{"year":2013,"finding":"N-glycosylation of ICAM-2 at its six N-linked glycosylation sites is required for complete suppression of neuroblastoma metastatic potential in vivo. Hypo- or non-glycosylated ICAM-2 variants attenuate but do not abolish metastasis suppression.","method":"Site-directed mutagenesis of glycosylation sites (Asn-to-Ala), in vitro motility and colony growth assays, in vivo metastasis model","journal":"BMC cancer","confidence":"Medium","confidence_rationale":"Tier 2 — systematic mutagenesis of glycosylation sites with in vivo validation; single lab","pmids":["23714211"],"is_preprint":false},{"year":2001,"finding":"Crystals of the complex between the radixin FERM domain and the full-length cytoplasmic tail of ICAM-2 (28-residue peptide) were obtained and characterized, with data to 2.60 Å, establishing structural compatibility of the ERM-ICAM-2 cytoplasmic tail interaction.","method":"X-ray crystallography of radixin FERM domain – ICAM-2 cytoplasmic tail complex (crystal characterization paper)","journal":"Acta crystallographica. Section D, Biological crystallography","confidence":"Medium","confidence_rationale":"Tier 1 — structural crystallography but only crystal characterization reported, not full structure","pmids":["11375520"],"is_preprint":false},{"year":2008,"finding":"ICAM-2 silencing by siRNA in oral squamous cell carcinoma cells enhances radiosensitivity and increases apoptosis via phosphorylation of AKT (Ser473) and activation of caspase-3. Conversely, ICAM-2 overexpression increases radioresistance, indicating ICAM-2 promotes cell survival through the AKT/caspase-3 pathway.","method":"siRNA knockdown and overexpression of ICAM-2, clonogenic radiosensitivity assay, flow cytometry for apoptosis, Western blot for phospho-AKT and caspase-3","journal":"British journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2 — gain- and loss-of-function with defined biochemical readouts; single lab","pmids":["18349842"],"is_preprint":false},{"year":1998,"finding":"ICAM-2 provides LFA-1-dependent co-stimulation to T cells beyond merely enhancing adhesion: ICAM-1 or ICAM-2 expression on fibroblast antigen-presenting cells increases T cell proliferation and, critically, enables a secondary allogeneic T cell response, indicating ICAM-2 delivers a co-stimulatory signal that prevents T cell anergy.","method":"ICAM-1 or ICAM-2 transfected fibroblasts as APCs, T cell proliferation (thymidine incorporation), primary/secondary allogeneic stimulation design, LFA-1 blocking antibody","journal":"Scandinavian journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 — defined functional outcome with blocking controls and primary/secondary response design; single lab","pmids":["9122613"],"is_preprint":false},{"year":2023,"finding":"ICAM-2 on leptomeningeal metastatic TNBC cells promotes blood-CSF barrier (BCB) adhesion, trans-BCB migration, and stemness via direct interaction with ICAM-1 on choroid plexus epithelial cells. Pull-down and antibody neutralization assays demonstrated ICAM2-ICAM1 interaction determines leptomeningeal metastasis specificity.","method":"Proteomic analysis, pull-down assay, antibody neutralization, in vivo spinal cord colonization model, siRNA knockdown","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2-3 — pull-down and neutralization with in vivo validation; single lab, novel finding","pmids":["37620448"],"is_preprint":false},{"year":2022,"finding":"ATT (artemisitene) inhibits ICAM2 expression via suppression of METTL3-mediated N6-methyladenosine (m6A) methylation of ICAM2 mRNA in RA fibroblast-like synoviocytes. ICAM2 acts as a promoter of RA-FLS proliferation, migration, and invasion through the PI3K/AKT/p300 pathway. p300 directly facilitates METTL3 transcription, forming a METTL3/ICAM2/PI3K/AKT/p300 feedback loop.","method":"RNA-seq, methylated RNA immunoprecipitation (MeRIP), chromatin immunoprecipitation (ChIP), plasmid/lentivirus overexpression, siRNA knockdown, Western blot, CIA mouse model","journal":"Clinical and translational medicine","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal molecular methods demonstrating m6A regulation of ICAM2 mRNA and downstream signaling; single lab","pmids":["36536495"],"is_preprint":false}],"current_model":"ICAM-2 is a two-Ig-domain transmembrane glycoprotein that functions as a constitutively expressed ligand for the leukocyte integrins LFA-1 (CD11a/CD18) and Mac-1 (CD11b/CD18) — binding LFA-1 via a flat ridge on the GFC β-sheet of domain 1 with Glu-37 coordinating Mg²⁺ in the integrin I domain — and as a ligand for DC-SIGN via Lewis Y glycans; intracellularly, its positively charged juxta-membrane cytoplasmic tail binds ERM proteins (ezrin/radixin/moesin) in a PtdIns(4,5)P2-regulated manner and alpha-actinin, linking it to the actin cytoskeleton; ERM-mediated redistribution of ICAM-2 to uropods confers NK cell sensitivity, while cytoplasmic tail signaling activates the PI3K/AKT pathway (via ezrin phosphorylation) to promote cell survival, and activates Rac-1 to regulate angiogenesis and vascular barrier function; on endothelium, ICAM-2 is transcriptionally driven by Sp1, GATA, and Ets (Erg) factors and is down-regulated by TNF-α/IL-1β, and it mediates sequential steps of leukocyte extravasation — particularly neutrophil and T cell crawling and diapedesis — in a manner distinct from but partly redundant with ICAM-1."},"narrative":{"teleology":[{"year":1989,"claim":"The discovery of ICAM-2 as a second LFA-1 ligand resolved why LFA-1-dependent adhesion persisted in the presence of saturating ICAM-1 blockade, establishing a new immunoglobulin superfamily member with two Ig-like domains.","evidence":"Functional cloning from COS cells with cell adhesion assays","pmids":["2497351"],"confidence":"High","gaps":["No structural information on binding interface","Expression pattern across tissues not fully characterized"]},{"year":1991,"claim":"Characterization of ICAM-2 protein and a blocking monoclonal antibody established that ICAM-2 is constitutively expressed on endothelium and accounts for LFA-1-dependent adhesion to both resting and activated endothelium alongside ICAM-1.","evidence":"Monoclonal antibody CBR-IC2/2 blocking, immunoprecipitation, N-glycanase treatment, cell binding assays","pmids":["1676048"],"confidence":"High","gaps":["Mac-1 binding not yet tested","Cytoplasmic interactions unknown"]},{"year":1995,"claim":"Identification of Mac-1 (CD11b/CD18) as a second integrin receptor for ICAM-2, binding through the CD11b A domain, broadened ICAM-2's role beyond LFA-1 to include myeloid cell interactions.","evidence":"Cell binding assays with purified CD11b/CD18, A-domain blocking","pmids":["7561061"],"confidence":"High","gaps":["Relative affinity of Mac-1 vs. LFA-1 for ICAM-2 not quantified","In vivo relevance of Mac-1–ICAM-2 not yet demonstrated"]},{"year":1997,"claim":"The crystal structure of the ICAM-2 extracellular domain revealed a flat LFA-1 recognition surface on the GFC β-sheet of domain 1 with Glu-37 as the critical Mg²⁺-coordinating residue, providing the first atomic-level view of an ICAM–integrin interface.","evidence":"X-ray crystallography of ICAM-2 ectodomain, validated by subsequent site-directed mutagenesis","pmids":["9153399","10077629"],"confidence":"High","gaps":["No co-crystal with LFA-1 I domain","Domain 2 contribution to binding unclear"]},{"year":1996,"claim":"Discovery that the ICAM-2 cytoplasmic tail binds α-actinin and ERM proteins linked this adhesion molecule to the actin cytoskeleton and revealed that ezrin-driven redistribution of ICAM-2 to uropods confers NK cell sensitivity.","evidence":"Affinity pulldown with cytoplasmic peptide, colocalization, ezrin transfection into NK-resistant targets with cytotoxicity assays","pmids":["8824270","8717043"],"confidence":"High","gaps":["Relative contributions of α-actinin vs. ERM binding to cellular function not separated","Structural basis of cytoplasmic tail–ERM interaction not resolved"]},{"year":1998,"claim":"Quantitative biochemistry established the ezrin–ICAM-2 interaction (KD ~330 nM) and showed PtdIns(4,5)P₂ enhances this binding, identifying ICAM-2 as the first adhesion molecule with a PIP₂-regulated cytoskeletal linkage; in parallel, ICAM-2 was shown to co-stimulate T cells via LFA-1 and to mediate T cell transendothelial migration on ICAM-1-deficient endothelium.","evidence":"SPR, affinity precipitation, PIP₂ binding assays; T cell proliferation assays with transfected APCs; transendothelial migration using ICAM-1-KO endothelioma","pmids":["9705328","9122613","9808177"],"confidence":"High","gaps":["Full structure of ERM–ICAM-2 complex not yet solved","Whether PIP₂ regulation occurs in vivo on endothelium not tested"]},{"year":1998,"claim":"Mapping of the ICAM-2 promoter identified Sp1, GATA, and Ets (Erg) binding sites as critical for endothelial-specific expression, establishing the transcriptional basis for constitutive ICAM-2 expression on vascular endothelium.","evidence":"Reporter gene assays, site-directed mutagenesis of promoter, EMSA with endothelial nuclear extracts","pmids":["9565596"],"confidence":"High","gaps":["Chromatin-level regulation (histone marks, accessibility) not addressed","Whether the same elements drive expression in non-endothelial lineages unknown"]},{"year":1999,"claim":"TNF-α and IL-1β were shown to transcriptionally down-regulate ICAM-2 via reduction of Erg binding to promoter Ets sites, explaining how inflammation reciprocally regulates ICAM-1 (up) and ICAM-2 (down) on endothelium; separately, ICAM-2-deficient mice revealed a non-redundant role in eosinophil transmigration and megakaryopoiesis.","evidence":"Promoter mutagenesis, EMSA, Erg protein levels by Western blot; ICAM-2-KO mice with allergic lung inflammation model and bone marrow chimeras","pmids":["10574717","10223354","10023766"],"confidence":"High","gaps":["Mechanism of Erg downregulation by TNF-α not elucidated","Megakaryopoiesis phenotype not mechanistically dissected"]},{"year":2002,"claim":"ICAM-2 was found to activate the PI3K/AKT survival pathway through ezrin phosphorylation, protecting B cells from apoptosis and establishing ICAM-2 as a signaling receptor, not merely a passive ligand; notably, ICAM-2 does not activate RhoA, distinguishing its signaling from ICAM-1.","evidence":"ICAM-2 clustering, phosphorylation cascades (ezrin/AKT/BAD/GSK3/FKHR), apoptosis protection assays; RhoA activity assays comparing ICAM-1 and ICAM-2 cross-linking","pmids":["11825565","12097408"],"confidence":"High","gaps":["Direct kinase linking ezrin phosphorylation to PI3K recruitment unknown","Whether AKT signaling is relevant in endothelial context not shown"]},{"year":2005,"claim":"Genetic deletion demonstrated that endothelial ICAM-2 promotes angiogenesis through Rac-1 activation, supporting tube formation, migration, and cell survival — establishing a vascular morphogenesis function beyond leukocyte adhesion.","evidence":"ICAM-2-deficient mice and endothelial cells, in vitro and in vivo angiogenesis models, Rac GTPase activity assays","pmids":["15920013"],"confidence":"High","gaps":["Upstream activator of Rac-1 downstream of ICAM-2 not identified","Whether homophilic ICAM-2 interaction is direct or indirect unclear"]},{"year":2008,"claim":"DC-SIGN was identified as a glycan-dependent receptor for ICAM-2 via Lewis Y epitopes, establishing ICAM-2 as a scaffold for dendritic cell rolling on endothelium; separately, ICAM-2 expression was shown to suppress neuroblastoma metastasis through α-actinin-mediated actin reorganization.","evidence":"DC-SIGN binding assays with glycosylation mutants, FUT1 siRNA, rolling assays under flow; co-IP and competitive peptide assays with in vivo metastasis model","pmids":["18155766","18978946"],"confidence":"High","gaps":["Whether Lewis Y glycosylation of ICAM-2 varies by vascular bed in vivo unknown","Metastasis suppression mechanism beyond actin reorganization not defined"]},{"year":2010,"claim":"Systematic genetic dissection using single and double ICAM-1/ICAM-2 knockouts under physiological flow revealed that ICAM-2 specifically mediates leukocyte crawling and diapedesis (but not arrest) at the blood-brain barrier, acting sequentially with ICAM-1, JAM-A, and PECAM-1.","evidence":"Live imaging under flow with WT, ICAM-1-KO, ICAM-2-KO, and double-KO primary brain endothelial cells; intravital imaging in KO mice","pmids":["20861356","19211506","24259506"],"confidence":"High","gaps":["Whether ICAM-2 signals to endothelial cells during crawling or only serves as a passive track unknown","Contribution at non-CNS vascular beds less well dissected"]},{"year":2014,"claim":"ICAM-2 was shown to regulate vascular barrier function through its cytoplasmic ERM-binding domain, activating Rac-1 to maintain N-cadherin junctions; deficiency increased thrombin-induced permeability in vivo, unifying its Rac-1 signaling role across angiogenesis and barrier maintenance.","evidence":"ICAM-2 domain mutants (ΔERM, ΔTAIL), constitutively active Rac-1 rescue, transendothelial resistance, intravital albumin extravasation in ICAM-2-KO mice","pmids":["24593809"],"confidence":"High","gaps":["GEF linking ICAM-2/ERM to Rac-1 activation not identified","Relationship between barrier and angiogenesis phenotypes not integrated"]},{"year":2022,"claim":"METTL3-mediated m6A methylation of ICAM2 mRNA was identified as an epitranscriptomic regulatory mechanism, with ICAM-2 promoting RA fibroblast-like synoviocyte pathology through PI3K/AKT/p300 in a positive feedback loop.","evidence":"MeRIP, ChIP for p300 at METTL3 promoter, siRNA and overexpression, CIA mouse model","pmids":["36536495"],"confidence":"Medium","gaps":["m6A regulation of ICAM2 not confirmed in endothelial or immune cell contexts","Whether m6A modification affects ICAM-2 protein level versus translation efficiency not resolved","Single-lab finding"]},{"year":null,"claim":"Key open questions include: the identity of the GEF linking ICAM-2/ERM to Rac-1; whether ICAM-2 homophilic interactions are direct; the structural basis of the full radixin FERM–ICAM-2 cytoplasmic tail complex; and the physiological significance of differential glycosylation of ICAM-2 across cell types.","evidence":"","pmids":[],"confidence":"High","gaps":["No co-crystal structure of ICAM-2 with LFA-1 or radixin FERM domain","GEF for ICAM-2-dependent Rac-1 activation unknown","In vivo relevance of differential glycosylation across vascular beds not tested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[0,1,2,12,22,24]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[6,7,9,20]},{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[0,1,2,18]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1,6,8,26]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[9,20]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,1,22,23,24,25,26]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[9,11,20,31]},{"term_id":"R-HSA-1500931","term_label":"Cell-Cell communication","supporting_discovery_ids":[0,1,22,24,26]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[9,31]}],"complexes":[],"partners":["ITGAL","ITGAM","EZR","RDX","MSN","ACTN1","CD209","ICAM1"],"other_free_text":[]},"mechanistic_narrative":"ICAM-2 is a constitutively expressed two-immunoglobulin-domain transmembrane glycoprotein that serves as an adhesion ligand on endothelium and hematopoietic cells, mediating leukocyte trafficking, vascular integrity, and cell survival signaling. Its extracellular domain 1 binds the leukocyte integrins LFA-1 (CD11a/CD18) and Mac-1 (CD11b/CD18) via a flat ridge on the GFC β-sheet centered on Glu-37, which coordinates Mg²⁺ in the integrin I domain, and also engages DC-SIGN through Lewis Y glycans [PMID:9153399, PMID:10077629, PMID:7561061, PMID:18155766]. Its short cytoplasmic tail links to the actin cytoskeleton through direct binding of ERM proteins (regulated by PtdIns(4,5)P₂) and α-actinin, and transduces signals activating PI3K/AKT to promote cell survival and Rac-1 to regulate angiogenesis and endothelial barrier function [PMID:9705328, PMID:8824270, PMID:11825565, PMID:15920013, PMID:24593809]. On inflamed endothelium, ICAM-2 acts sequentially with ICAM-1, JAM-A, and PECAM-1 to mediate neutrophil and T cell crawling and diapedesis, with genetic deficiency impairing leukocyte extravasation and increasing vascular permeability in vivo [PMID:20861356, PMID:24259506, PMID:24317296, PMID:10023766]."},"prefetch_data":{"uniprot":{"accession":"P13598","full_name":"Intercellular adhesion molecule 2","aliases":[],"length_aa":275,"mass_kda":30.7,"function":"Cell adhesion molecule that functions as a receptor ligand of the signaling receptor ITGAL:ITGB2/LFA-1 (lymphocyte-function associated (LFA) molecule 1) ensuring leukocyte cell-cell adhesion on resting cells (PubMed:10077629, PubMed:1676048, PubMed:2497351). Also endothelial blood vessels receptor ligand of dendritic cell (DC) CD209 signaling receptor that mediates triggering transendothelial migration of DC presursors from blood into peripheral tissues and, subsequently, into lymphoid tissues (PubMed:11017109). Mediates adhesive interactions important for antigen presentation, lymphocyte recirculation, and other cellular interactions important for immune response and surveillance (Probable)","subcellular_location":"Cell membrane; Cell projection, microvillus","url":"https://www.uniprot.org/uniprotkb/P13598/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ICAM2","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ICAM2","total_profiled":1310},"omim":[{"mim_id":"614088","title":"INTRACELLULAR ADHESION MOLECULE 4; ICAM4","url":"https://www.omim.org/entry/614088"},{"mim_id":"603693","title":"ZINC FINGER PROTEIN, FOG FAMILY MEMBER 2; ZFPM2","url":"https://www.omim.org/entry/603693"},{"mim_id":"602731","title":"FYN-BINDING PROTEIN 1; FYB1","url":"https://www.omim.org/entry/602731"},{"mim_id":"602037","title":"RAS HOMOLOG GENE FAMILY, MEMBER H; RHOH","url":"https://www.omim.org/entry/602037"},{"mim_id":"600576","title":"GATA-BINDING PROTEIN 4; GATA4","url":"https://www.omim.org/entry/600576"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"lymphoid tissue","ntpm":156.5}],"url":"https://www.proteinatlas.org/search/ICAM2"},"hgnc":{"alias_symbol":["CD102"],"prev_symbol":[]},"alphafold":{"accession":"P13598","domains":[{"cath_id":"2.60.40.10","chopping":"28-107","consensus_level":"high","plddt":95.4393,"start":28,"end":107},{"cath_id":"2.60.40.10","chopping":"115-215","consensus_level":"high","plddt":93.168,"start":115,"end":215}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P13598","model_url":"https://alphafold.ebi.ac.uk/files/AF-P13598-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P13598-F1-predicted_aligned_error_v6.png","plddt_mean":87.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ICAM2","jax_strain_url":"https://www.jax.org/strain/search?query=ICAM2"},"sequence":{"accession":"P13598","fasta_url":"https://rest.uniprot.org/uniprotkb/P13598.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P13598/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P13598"}},"corpus_meta":[{"pmid":"2497351","id":"PMC_2497351","title":"Functional cloning of ICAM-2, a cell adhesion ligand for LFA-1 homologous to ICAM-1.","date":"1989","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/2497351","citation_count":855,"is_preprint":false},{"pmid":"9472040","id":"PMC_9472040","title":"Ezrin/radixin/moesin (ERM) proteins bind to a positively charged amino acid cluster in the juxta-membrane cytoplasmic domain of CD44, CD43, and ICAM-2.","date":"1998","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/9472040","citation_count":519,"is_preprint":false},{"pmid":"1676048","id":"PMC_1676048","title":"Characterization of ICAM-2 and evidence for a third counter-receptor for LFA-1.","date":"1991","source":"The Journal of experimental medicine","url":"https://pubmed.ncbi.nlm.nih.gov/1676048","citation_count":499,"is_preprint":false},{"pmid":"9705328","id":"PMC_9705328","title":"Association of ezrin with intercellular adhesion molecule-1 and -2 (ICAM-1 and ICAM-2). 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Expressed and Up-Regulated on Inflamed Pulmonary Epithelium, but Neither ICAM-2 nor LFA-1: ICAM-1 Are Required for Neutrophil Migration Into the Airways In Vivo.","date":"2021","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/34484188","citation_count":27,"is_preprint":false},{"pmid":"1709118","id":"PMC_1709118","title":"ICAM-2 peptides mediate lymphocyte adhesion by binding to CD11a/CD18 and CD49d/CD29 integrins.","date":"1991","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/1709118","citation_count":27,"is_preprint":false},{"pmid":"7684421","id":"PMC_7684421","title":"EBV peptide epitope sensitization restores human cytotoxic T cell recognition of Burkitt's lymphoma cells. 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biology","url":"https://pubmed.ncbi.nlm.nih.gov/36543997","citation_count":11,"is_preprint":false},{"pmid":"9122613","id":"PMC_9122613","title":"ICAM-2 provides a costimulatory signal for T cell stimulation by allogeneic class II MHC.","date":"1997","source":"Scandinavian journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/9122613","citation_count":11,"is_preprint":false},{"pmid":"37620448","id":"PMC_37620448","title":"ICAM2 initiates trans-blood-CSF barrier migration and stemness properties in leptomeningeal metastasis of triple-negative breast cancer.","date":"2023","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/37620448","citation_count":8,"is_preprint":false},{"pmid":"32612609","id":"PMC_32612609","title":"Novel MHC-Independent αβTCRs Specific for CD48, CD102, and CD155 Self-Proteins and Their Selection in the Thymus.","date":"2020","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/32612609","citation_count":7,"is_preprint":false},{"pmid":"14611686","id":"PMC_14611686","title":"Intercellular adhesion molecule-2 (ICAM-2) and Pseudomonas aeruginosa ocular infection.","date":"2003","source":"DNA and cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/14611686","citation_count":7,"is_preprint":false},{"pmid":"11375520","id":"PMC_11375520","title":"Crystallographic characterization of the radixin FERM domain bound to the cytoplasmic tail of the adhesion protein ICAM-2.","date":"2001","source":"Acta crystallographica. 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ICAM-2 is an integral membrane protein with two immunoglobulin-like domains, most closely related to the two N-terminal domains of ICAM-1 (34% identity), and supports LFA-1-dependent cell adhesion.\",\n      \"method\": \"Functional cloning using a novel ligand identification method; transfection of COS cells with ICAM-2 cDNA and cell adhesion assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — original functional cloning with cell adhesion assays, highly cited foundational paper\",\n      \"pmids\": [\"2497351\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"ICAM-2 binds LFA-1; monoclonal antibody CBR-IC2/2 totally inhibits ICAM-2+ cell binding to purified LFA-1. ICAM-2 accounts for LFA-1-dependent adhesion to both stimulated and unstimulated endothelium together with ICAM-1. ICAM-2 has a peptide backbone of ~31 kDa (Mr ~60,000 as a broad glycosylated band), and is constitutively expressed on endothelium and hematopoietic cells with little inflammatory induction.\",\n      \"method\": \"Monoclonal antibody generation, immunoprecipitation, N-glycanase treatment, cell binding assays to purified LFA-1\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — blocking mAb, biochemical characterization, replicated functional adhesion assays\",\n      \"pmids\": [\"1676048\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"ICAM-2 (CD102) binds to the leukocyte integrin CD11b/CD18 (Mac-1) through the CD11b A domain, in addition to its known interaction with CD11a/CD18 (LFA-1).\",\n      \"method\": \"Cell binding assays with purified CD11b/CD18; domain-specific blocking experiments using A-domain constructs\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct binding demonstrated with purified protein and domain-level mapping\",\n      \"pmids\": [\"7561061\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Crystal structure of ICAM-2 extracellular region was solved. Glu-37 is critical for LFA-1 binding and is proposed to coordinate Mg2+ in the LFA-1 I domain. The LFA-1 recognition surface is relatively flat, lying on the GFC beta-sheet of domain 1, contrasting with loop-presented acidic residues in non-I-domain integrin ligands. A bend between domains 1 and 2 and N-linked glycan tripod arrangement may orient the recognition surface.\",\n      \"method\": \"X-ray crystallography of ICAM-2 extracellular domain\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with functional interpretation; independently validated by mutagenesis in subsequent work\",\n      \"pmids\": [\"9153399\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Mutagenesis of ICAM-2 based on its crystal structure mapped the LFA-1 binding site to a diagonal ridge across the GFC beta-sheet including the CD edge of domain 1. Glu-37 ligates the Mg2+ in the LFA-1 I domain. The site is oblong and confined to the upper part of domain 1, distinct from the VCAM-1 binding surface for alpha4 integrins.\",\n      \"method\": \"Site-directed mutagenesis of ICAM-2 combined with cell adhesion assays and structural interpretation\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis validated crystal structure, multiple mutants tested\",\n      \"pmids\": [\"10077629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"ICAM-2 binds alpha-actinin through its cytoplasmic domain (residues 231-254, with optimal binding at amino acids 241-248). Alpha-actinin colocalized with ICAM-2 in endothelial cells. Multiple regions of alpha-actinin can mediate this interaction.\",\n      \"method\": \"Affinity pulldown using ICAM-2 cytoplasmic peptide as matrix from placental lysates, immunoblotting, 125I-labeled alpha-actinin binding, confocal microscopy colocalization, overlapping octapeptide competition, bacterially expressed alpha-actinin domain fusion proteins\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro reconstitution with purified proteins, domain mapping, colocalization; multiple orthogonal methods\",\n      \"pmids\": [\"8824270\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"ERM proteins (ezrin/radixin/moesin) bind directly to a positively charged amino acid cluster in the juxta-membrane cytoplasmic domain of ICAM-2 (28 amino acids). This binding concentrates ICAM-2 at microvilli. Site-directed mutagenesis of these clusters abolishes ERM binding.\",\n      \"method\": \"GST fusion protein pulldown (in vitro binding), immunoprecipitation, chimeric E-cadherin construct expression in L fibroblasts, site-directed mutagenesis, colocalization by microscopy\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods including mutagenesis and reconstitution in cells\",\n      \"pmids\": [\"9472040\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Ezrin interacts directly with ICAM-2 cytoplasmic tail with a KD of 3.3×10^-7 M. ICAM-2 colocalizes with ezrin in microvillar projections in transfected cells. Phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) enhances the ezrin–ICAM-2 interaction and binds to the ICAM-2 cytoplasmic tail, identifying ICAM-2 as the first adhesion protein shown to interact with PtdIns(4,5)P2.\",\n      \"method\": \"Affinity precipitation, microtiter binding assay, co-immunoprecipitation, surface plasmon resonance, PtdIns(4,5)P2 binding assays, confocal colocalization in transfected cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — SPR gives quantitative KD, multiple orthogonal methods, novel biochemical finding replicated across methods\",\n      \"pmids\": [\"9705328\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"ICAM-2 redistribution to uropods (bud-like projections) by ezrin confers NK cell sensitivity to target cells. Ezrin transfection into NK-resistant cells induces uropod formation, redistributes ICAM-2 from uniform surface distribution to concentrated uropods, and sensitizes targets to IL-2-activated NK killing.\",\n      \"method\": \"Transfection of ezrin into NK-resistant cells, fluorescence imaging of ICAM-2/ezrin localization, NK cytotoxicity assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct functional consequence of localization change demonstrated by transfection and cytotoxicity assay; published in Nature\",\n      \"pmids\": [\"8717043\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"ICAM-2 activates the PI3K/AKT pathway. ICAM-2 induces tyrosine phosphorylation of ezrin and PI3K membrane translocation, leading to PtdIns(3,4,5)P3 production, PDK-1 and AKT activation, and phosphorylation of AKT substrates BAD, GSK3, and FKHR. ICAM-2 clustering protects primary human CD19+ B cells from TNFα- and Fas-mediated apoptosis. ICAM-2 engagement by LFA-1 on CD4+ T cells induces AKT activity in CD19+ cells in the absence of MHC-peptide interaction.\",\n      \"method\": \"Genetic screen, reporter assays, biochemical signaling assays (phosphorylation of ezrin, AKT, BAD, GSK3, FKHR), single-cell analysis of apoptosis, ICAM-2 clustering experiments\",\n      \"journal\": \"Immunity\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple downstream signaling nodes measured, mechanistic pathway mapped, functional apoptosis protection demonstrated\",\n      \"pmids\": [\"11825565\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"ICAM-1 cross-linking activates RhoA and induces stress fiber formation in endothelial cells, and stimulates c-fos and rhoA transcription, while ICAM-2 cross-linking does not activate RhoA or alter actin organization, demonstrating distinct downstream signaling despite both colocalizing with moesin in microvilli.\",\n      \"method\": \"Antibody cross-linking of ICAM-1 and ICAM-2 in HUVECs, RhoA activity assay, confocal microscopy, reporter gene assays for c-fos and rhoA transcription\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct comparison with functional GTPase assays and transcriptional reporters, multiple methods\",\n      \"pmids\": [\"12097408\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Endothelial ICAM-2 mediates angiogenesis. ICAM-2-deficient mice and cells show impaired angiogenesis in vitro and in vivo. ICAM-2 supports homophilic interaction involved in tube formation. ICAM-2-deficient cells show defective migration and increased apoptosis. ICAM-2 activates the small GTPase Rac, required for tube formation and migration.\",\n      \"method\": \"ICAM-2-deficient mice and endothelial cells, in vitro tube formation and migration assays, in vivo angiogenesis models, Rac GTPase activity assays, apoptosis assays\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with multiple phenotypic readouts, GTPase assay, in vitro and in vivo validation\",\n      \"pmids\": [\"15920013\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"A synthetic peptide from ICAM-2 spanning residues 21-42 of the first immunoglobulin domain binds specifically to purified CD11a/CD18 (LFA-1), inhibits adhesion of endothelial cells to LFA-1, and inhibits B lymphoblastoid cell binding to endothelial cells. Leukocytes bind this peptide when coated on plastic.\",\n      \"method\": \"Synthetic peptide binding assay to purified CD11a/CD18, cell adhesion inhibition assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct binding to purified integrin, functional inhibition demonstrated\",\n      \"pmids\": [\"8349630\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"An ICAM-2 peptide (residues 21-42) activates NK cell migration by 215% via CD11a/CD18 (LFA-1) ligation, induces F-actin polymerization at the leading edge of migratory NK cells, and increases phosphorylation of 150-kDa and 35-kDa proteins. Ligation of LFA-1 via ICAM-2 peptide transmits signals distinct from antibody cross-linking, triggering locomotion without necessarily triggering cytotoxicity.\",\n      \"method\": \"Boyden chamber migration assay, anti-CD11a antibody blocking, F-actin staining, phosphotyrosine immunoblotting\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean functional assays with inhibitor controls and biochemical readouts from single lab\",\n      \"pmids\": [\"7721764\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"ICAM-2 (and a peptide from its LFA-1 binding domain) activates leukocyte adhesion by increasing integrin affinity (inside-out signaling): soluble ICAM-2Fc induces T lymphocyte adhesion to immobilized ICAMs more potently than ICAM-1Fc or ICAM-3Fc, and stimulates binding of soluble recombinant ICAMs to T lymphocytes. The effect requires energy, divalent cations, temperature, and an intact cytoskeleton.\",\n      \"method\": \"T lymphocyte adhesion assays to immobilized purified ICAMs, flow cytometry for soluble ICAM binding, inhibitor studies (cytoskeletal, kinase inhibitors)\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple assay types, mechanistic inhibitor controls, single lab\",\n      \"pmids\": [\"10352278\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"The ICAM-2 promoter is endothelial cell-specific in vitro and in vivo. Critical Sp1 motif at -194 and eight-base pair palindrome at -268 each contribute ~70% of promoter activity. GATA motifs at -145 and -53 each contribute ~61-78%. The Ets family member Erg constitutively binds the ICAM-2 promoter in endothelial cells and transactivates it.\",\n      \"method\": \"Reporter gene assays, site-directed mutagenesis of promoter elements, gel shift (EMSA) with endothelial nuclear proteins, GATA-2 overexpression transactivation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — mutagenesis of specific regulatory elements with reporter assays and EMSA validation\",\n      \"pmids\": [\"9565596\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"TNF-α and IL-1β down-regulate ICAM-2 expression on endothelium at the transcriptional level by reducing ICAM-2 mRNA to ~40% of control and decreasing ICAM-2 promoter activity. This correlates with loss of ICAM-2 protein from endothelial cell junctions.\",\n      \"method\": \"Flow cytometry, Northern blotting, ICAM-2 promoter reporter assay in HUVECs, immunocytochemistry\",\n      \"journal\": \"Cell adhesion and communication\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (mRNA, protein, promoter activity) from single lab\",\n      \"pmids\": [\"10223354\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"TNF-α-mediated down-regulation of ICAM-2 transcription involves three Ets binding sites (EBS) in the promoter. TNF-α decreases binding of nuclear proteins to the -135/-127 EBS. The Ets factor Erg constitutively transactivates the ICAM-2 promoter and is down-regulated by TNF-α, linking Erg to ICAM-2 transcriptional regulation.\",\n      \"method\": \"Site-directed mutagenesis of promoter Ets sites, EMSA, Erg cDNA transactivation assays in HeLa and HUVEC, Western blot for Erg protein, ex vivo artery model\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — mutagenesis, EMSA, overexpression transactivation, and ex vivo validation; multiple orthogonal methods\",\n      \"pmids\": [\"10574717\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"DC-SIGN binds ICAM-2 via a carbohydrate-dependent interaction. DC-SIGN mediates adhesion and rolling of dendritic cells on primary endothelial cells through the Lewis Y (Le^Y) glycan epitope expressed on ICAM-2. ICAM-2 expressed on CHO cells only serves as a DC-SIGN ligand when properly glycosylated, demonstrating ICAM-2 acts as a scaffold. The Le^Y-presenting enzyme FUT1 directs this endothelial expression; FUT1 silencing reduces DC rolling and adhesion.\",\n      \"method\": \"Recombinant soluble DC-SIGN binding assays, alanine-scanning mutagenesis of DC-SIGN, CHO cell expression of ICAM-2, FUT1 siRNA knockdown, rolling/adhesion assays under shear flow, glycan chip analysis\",\n      \"journal\": \"Molecular immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — mutagenesis, glycan manipulation, siRNA, functional flow assays; multiple orthogonal methods\",\n      \"pmids\": [\"18155766\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Physiologic sialylation of platelet ICAM-2 (more acidic pI due to N-linked glycosylation) renders it ~50% less able to support LFA-1-dependent T cell adhesion compared to endothelial ICAM-2, and unable to support DC-SIGN-mediated dendritic cell adhesion. Neuraminidase treatment abolishes these functional differences.\",\n      \"method\": \"Isoelectric focusing of ICAM-2 from platelets vs. HUVECs, N-glycanase and neuraminidase treatment, T cell adhesion assays, DC adhesion assays\",\n      \"journal\": \"Inflammation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — enzymatic treatments with matched functional adhesion assays, cell-type comparison, single lab\",\n      \"pmids\": [\"15673159\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"ICAM-2 regulates endothelial barrier function and vascular permeability through a pathway involving N-cadherin, ERM proteins, and Rac-1 activation. The ERM-binding domain and cytoplasmic tail of ICAM-2 are required for junction formation and contact inhibition. Constitutively active Rac-1 restores barrier function in ICAM-2-deficient cells. In vivo, ICAM-2-deficient mice show increased thrombin-induced vascular permeability.\",\n      \"method\": \"ICAM-2 siRNA knockdown, ICAM-2-deficient endothelioma lines, re-expression of full-length and mutant ICAM-2 constructs (ΔERM, ΔTAIL), transendothelial electrical resistance measurement, constitutively active Rac-1 rescue, in vivo intravital fluorescence microscopy for albumin extravasation in mouse cremaster\",\n      \"journal\": \"Cell communication and signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO, domain mutants, rescue experiments, in vitro and in vivo validation with multiple readouts\",\n      \"pmids\": [\"24593809\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"ICAM-2 deficiency in mice causes prolonged eosinophil accumulation in the lung interstitium during allergic inflammation, delayed transfer to airway lumen, and prolonged airway hyperresponsiveness. This phenotype is caused by lack of ICAM-2 on non-hematopoietic (endothelial) cells, and ICAM-2 deficiency on endothelium directly reduces eosinophil transmigration in vitro. ICAM-2 is also required for normal megakaryocyte progenitor numbers.\",\n      \"method\": \"ICAM-2-deficient mice (genetic KO), allergic lung inflammation model, histological analysis, bone marrow chimeras to identify non-hematopoietic requirement, in vitro transmigration assays, airway hyperresponsiveness measurement\",\n      \"journal\": \"Immunity\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with bone marrow chimeras to dissect cell type, in vitro transmigration, multiple phenotypic readouts\",\n      \"pmids\": [\"10023766\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Endothelial ICAM-1 and ICAM-2 are both essential for transendothelial migration of T cells. In ICAM-1-deficient endothelium, only ICAM-2 mediates residual T cell transmigration; PECAM-1, VCAM-1, and E-selectin are not involved in this process.\",\n      \"method\": \"ICAM-1-deficient endothelioma cells from ICAM-1 mutant mice, retroviral rescue with ICAM-1, antibody blocking of ICAM-2 and other candidates, in vitro transendothelial migration assay\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO endothelium with retroviral rescue and antibody blocking; clean epistasis experiment\",\n      \"pmids\": [\"9808177\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Endothelial ICAM-2, JAM-A, and PECAM-1 mediate neutrophil transmigration sequentially. In a stimulus-dependent manner (IL-1β but not TNF-α), when neutrophils lack TNF-α receptor signaling, their transmigration becomes dependent on endothelial ICAM-2, JAM-A, and PECAM-1 acting in sequence, as demonstrated by localization of arrested neutrophils in single KO mice for each molecule.\",\n      \"method\": \"TNF-receptor-deficient leukocyte transfer into WT and single KO mice (ICAM-2-/-, JAM-A-/-, PECAM-1-/-), fluorescence intravital microscopy, site-of-arrest analysis\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo genetic epistasis with multiple KO mice and intravital imaging\",\n      \"pmids\": [\"19211506\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Endothelial ICAM-1 and VCAM-1 mediate shear-resistant T cell arrest, while endothelial ICAM-1 and ICAM-2 (but not VCAM-1) mediate T cell polarization and crawling at the BBB, establishing distinct and sequential roles. Endothelial ICAM-2 specifically contributes to the crawling step required for diapedesis.\",\n      \"method\": \"Live cell imaging under physiological flow; primary brain microvascular endothelial cells from WT, ICAM-1-deficient, ICAM-2-deficient, and ICAM-1/ICAM-2 double-deficient mice; analysis of T cell arrest, polarization, crawling, and diapedesis\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — live imaging under flow with multiple genetic KO combinations, dissects individual molecular contributions\",\n      \"pmids\": [\"20861356\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Beta-2 integrin-mediated neutrophil crawling on endothelial ICAM-1 and ICAM-2 is a prerequisite for transcellular neutrophil diapedesis across the inflamed BBB. LFA-1 primarily mediates shear-resistant arrest via ICAM-1, while Mac-1 dominates polarization. Both LFA-1 and Mac-1 mediate crawling via ICAM-1 and ICAM-2. Stationary (non-crawling) neutrophils cross exclusively via paracellular route.\",\n      \"method\": \"Live-cell imaging under flow; WT, CD11a-/-, CD11b-/-, CD18null neutrophils; WT, JAM-A-/-, ICAM-1null, ICAM-2-/-, ICAM-1null/ICAM-2-/- primary mouse BBB endothelial cells\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — comprehensive genetic dissection of integrin/ligand pairs with live imaging, multiple KO combinations\",\n      \"pmids\": [\"24259506\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"ICAM-2 is expressed both at EC junctions and on the EC body. Functional or genetic blockade of ICAM-2 reduces neutrophil crawling velocity, increases disrupted stop-start crawling, prolongs neutrophil interaction with EC junctions prior to TEM, and reduces overall extravasation in vivo. Some ICAM-2-dependent functions are mediated through Mac-1.\",\n      \"method\": \"Real-time in vivo confocal microscopy, ICAM-2-/- mice, functional antibody blockade, Mac-1 pharmacological inhibition, quantitative analysis of crawling parameters\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo genetic KO with real-time confocal imaging and pharmacological dissection\",\n      \"pmids\": [\"24317296\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"ICAM-2 forms a membrane-actin linkage with alpha-actinin and actin in neuroblastoma cells, as demonstrated by co-immunoprecipitation and competitive peptide assays. ICAM-2 expression limits neuroblastoma cell motility, redistributes actin, and suppresses disseminated metastatic tumors in vivo without affecting subcutaneous tumor growth.\",\n      \"method\": \"Co-immunoprecipitation, competitive peptide assays, in vitro migration assays, in vivo tail vein injection metastasis model, actin redistribution imaging, immunohistochemistry of primary tumors\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — co-IP with competitive peptide confirmation, in vivo model; multiple methods from single lab\",\n      \"pmids\": [\"18978946\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The interaction of ICAM-2 with alpha-actinin via its cytoplasmic domain is critical for ICAM-2-mediated suppression of the metastatic phenotype in neuroblastoma cells in vivo. ICAM-2 variants with mutated alpha-actinin-binding domains fail to completely suppress disseminated tumor development in vivo, despite retaining some inhibitory effects in vitro, indicating both alpha-actinin-dependent and -independent mechanisms.\",\n      \"method\": \"In silico domain modeling, expression of ICAM-2 alpha-actinin-binding domain mutants, co-precipitation assays, cell adhesion and migration assays, colony formation assays, in vivo tumor dissemination model\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — domain mutagenesis with in vivo validation; single lab\",\n      \"pmids\": [\"24704826\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"N-glycosylation of ICAM-2 at its six N-linked glycosylation sites is required for complete suppression of neuroblastoma metastatic potential in vivo. Hypo- or non-glycosylated ICAM-2 variants attenuate but do not abolish metastasis suppression.\",\n      \"method\": \"Site-directed mutagenesis of glycosylation sites (Asn-to-Ala), in vitro motility and colony growth assays, in vivo metastasis model\",\n      \"journal\": \"BMC cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — systematic mutagenesis of glycosylation sites with in vivo validation; single lab\",\n      \"pmids\": [\"23714211\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Crystals of the complex between the radixin FERM domain and the full-length cytoplasmic tail of ICAM-2 (28-residue peptide) were obtained and characterized, with data to 2.60 Å, establishing structural compatibility of the ERM-ICAM-2 cytoplasmic tail interaction.\",\n      \"method\": \"X-ray crystallography of radixin FERM domain – ICAM-2 cytoplasmic tail complex (crystal characterization paper)\",\n      \"journal\": \"Acta crystallographica. Section D, Biological crystallography\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — structural crystallography but only crystal characterization reported, not full structure\",\n      \"pmids\": [\"11375520\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"ICAM-2 silencing by siRNA in oral squamous cell carcinoma cells enhances radiosensitivity and increases apoptosis via phosphorylation of AKT (Ser473) and activation of caspase-3. Conversely, ICAM-2 overexpression increases radioresistance, indicating ICAM-2 promotes cell survival through the AKT/caspase-3 pathway.\",\n      \"method\": \"siRNA knockdown and overexpression of ICAM-2, clonogenic radiosensitivity assay, flow cytometry for apoptosis, Western blot for phospho-AKT and caspase-3\",\n      \"journal\": \"British journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — gain- and loss-of-function with defined biochemical readouts; single lab\",\n      \"pmids\": [\"18349842\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"ICAM-2 provides LFA-1-dependent co-stimulation to T cells beyond merely enhancing adhesion: ICAM-1 or ICAM-2 expression on fibroblast antigen-presenting cells increases T cell proliferation and, critically, enables a secondary allogeneic T cell response, indicating ICAM-2 delivers a co-stimulatory signal that prevents T cell anergy.\",\n      \"method\": \"ICAM-1 or ICAM-2 transfected fibroblasts as APCs, T cell proliferation (thymidine incorporation), primary/secondary allogeneic stimulation design, LFA-1 blocking antibody\",\n      \"journal\": \"Scandinavian journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — defined functional outcome with blocking controls and primary/secondary response design; single lab\",\n      \"pmids\": [\"9122613\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"ICAM-2 on leptomeningeal metastatic TNBC cells promotes blood-CSF barrier (BCB) adhesion, trans-BCB migration, and stemness via direct interaction with ICAM-1 on choroid plexus epithelial cells. Pull-down and antibody neutralization assays demonstrated ICAM2-ICAM1 interaction determines leptomeningeal metastasis specificity.\",\n      \"method\": \"Proteomic analysis, pull-down assay, antibody neutralization, in vivo spinal cord colonization model, siRNA knockdown\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — pull-down and neutralization with in vivo validation; single lab, novel finding\",\n      \"pmids\": [\"37620448\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ATT (artemisitene) inhibits ICAM2 expression via suppression of METTL3-mediated N6-methyladenosine (m6A) methylation of ICAM2 mRNA in RA fibroblast-like synoviocytes. ICAM2 acts as a promoter of RA-FLS proliferation, migration, and invasion through the PI3K/AKT/p300 pathway. p300 directly facilitates METTL3 transcription, forming a METTL3/ICAM2/PI3K/AKT/p300 feedback loop.\",\n      \"method\": \"RNA-seq, methylated RNA immunoprecipitation (MeRIP), chromatin immunoprecipitation (ChIP), plasmid/lentivirus overexpression, siRNA knockdown, Western blot, CIA mouse model\",\n      \"journal\": \"Clinical and translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal molecular methods demonstrating m6A regulation of ICAM2 mRNA and downstream signaling; single lab\",\n      \"pmids\": [\"36536495\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ICAM-2 is a two-Ig-domain transmembrane glycoprotein that functions as a constitutively expressed ligand for the leukocyte integrins LFA-1 (CD11a/CD18) and Mac-1 (CD11b/CD18) — binding LFA-1 via a flat ridge on the GFC β-sheet of domain 1 with Glu-37 coordinating Mg²⁺ in the integrin I domain — and as a ligand for DC-SIGN via Lewis Y glycans; intracellularly, its positively charged juxta-membrane cytoplasmic tail binds ERM proteins (ezrin/radixin/moesin) in a PtdIns(4,5)P2-regulated manner and alpha-actinin, linking it to the actin cytoskeleton; ERM-mediated redistribution of ICAM-2 to uropods confers NK cell sensitivity, while cytoplasmic tail signaling activates the PI3K/AKT pathway (via ezrin phosphorylation) to promote cell survival, and activates Rac-1 to regulate angiogenesis and vascular barrier function; on endothelium, ICAM-2 is transcriptionally driven by Sp1, GATA, and Ets (Erg) factors and is down-regulated by TNF-α/IL-1β, and it mediates sequential steps of leukocyte extravasation — particularly neutrophil and T cell crawling and diapedesis — in a manner distinct from but partly redundant with ICAM-1.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"ICAM-2 is a constitutively expressed two-immunoglobulin-domain transmembrane glycoprotein that serves as an adhesion ligand on endothelium and hematopoietic cells, mediating leukocyte trafficking, vascular integrity, and cell survival signaling. Its extracellular domain 1 binds the leukocyte integrins LFA-1 (CD11a/CD18) and Mac-1 (CD11b/CD18) via a flat ridge on the GFC β-sheet centered on Glu-37, which coordinates Mg²⁺ in the integrin I domain, and also engages DC-SIGN through Lewis Y glycans [PMID:9153399, PMID:10077629, PMID:7561061, PMID:18155766]. Its short cytoplasmic tail links to the actin cytoskeleton through direct binding of ERM proteins (regulated by PtdIns(4,5)P₂) and α-actinin, and transduces signals activating PI3K/AKT to promote cell survival and Rac-1 to regulate angiogenesis and endothelial barrier function [PMID:9705328, PMID:8824270, PMID:11825565, PMID:15920013, PMID:24593809]. On inflamed endothelium, ICAM-2 acts sequentially with ICAM-1, JAM-A, and PECAM-1 to mediate neutrophil and T cell crawling and diapedesis, with genetic deficiency impairing leukocyte extravasation and increasing vascular permeability in vivo [PMID:20861356, PMID:24259506, PMID:24317296, PMID:10023766].\",\n  \"teleology\": [\n    {\n      \"year\": 1989,\n      \"claim\": \"The discovery of ICAM-2 as a second LFA-1 ligand resolved why LFA-1-dependent adhesion persisted in the presence of saturating ICAM-1 blockade, establishing a new immunoglobulin superfamily member with two Ig-like domains.\",\n      \"evidence\": \"Functional cloning from COS cells with cell adhesion assays\",\n      \"pmids\": [\"2497351\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural information on binding interface\", \"Expression pattern across tissues not fully characterized\"]\n    },\n    {\n      \"year\": 1991,\n      \"claim\": \"Characterization of ICAM-2 protein and a blocking monoclonal antibody established that ICAM-2 is constitutively expressed on endothelium and accounts for LFA-1-dependent adhesion to both resting and activated endothelium alongside ICAM-1.\",\n      \"evidence\": \"Monoclonal antibody CBR-IC2/2 blocking, immunoprecipitation, N-glycanase treatment, cell binding assays\",\n      \"pmids\": [\"1676048\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mac-1 binding not yet tested\", \"Cytoplasmic interactions unknown\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Identification of Mac-1 (CD11b/CD18) as a second integrin receptor for ICAM-2, binding through the CD11b A domain, broadened ICAM-2's role beyond LFA-1 to include myeloid cell interactions.\",\n      \"evidence\": \"Cell binding assays with purified CD11b/CD18, A-domain blocking\",\n      \"pmids\": [\"7561061\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative affinity of Mac-1 vs. LFA-1 for ICAM-2 not quantified\", \"In vivo relevance of Mac-1–ICAM-2 not yet demonstrated\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"The crystal structure of the ICAM-2 extracellular domain revealed a flat LFA-1 recognition surface on the GFC β-sheet of domain 1 with Glu-37 as the critical Mg²⁺-coordinating residue, providing the first atomic-level view of an ICAM–integrin interface.\",\n      \"evidence\": \"X-ray crystallography of ICAM-2 ectodomain, validated by subsequent site-directed mutagenesis\",\n      \"pmids\": [\"9153399\", \"10077629\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No co-crystal with LFA-1 I domain\", \"Domain 2 contribution to binding unclear\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Discovery that the ICAM-2 cytoplasmic tail binds α-actinin and ERM proteins linked this adhesion molecule to the actin cytoskeleton and revealed that ezrin-driven redistribution of ICAM-2 to uropods confers NK cell sensitivity.\",\n      \"evidence\": \"Affinity pulldown with cytoplasmic peptide, colocalization, ezrin transfection into NK-resistant targets with cytotoxicity assays\",\n      \"pmids\": [\"8824270\", \"8717043\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contributions of α-actinin vs. ERM binding to cellular function not separated\", \"Structural basis of cytoplasmic tail–ERM interaction not resolved\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Quantitative biochemistry established the ezrin–ICAM-2 interaction (KD ~330 nM) and showed PtdIns(4,5)P₂ enhances this binding, identifying ICAM-2 as the first adhesion molecule with a PIP₂-regulated cytoskeletal linkage; in parallel, ICAM-2 was shown to co-stimulate T cells via LFA-1 and to mediate T cell transendothelial migration on ICAM-1-deficient endothelium.\",\n      \"evidence\": \"SPR, affinity precipitation, PIP₂ binding assays; T cell proliferation assays with transfected APCs; transendothelial migration using ICAM-1-KO endothelioma\",\n      \"pmids\": [\"9705328\", \"9122613\", \"9808177\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full structure of ERM–ICAM-2 complex not yet solved\", \"Whether PIP₂ regulation occurs in vivo on endothelium not tested\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Mapping of the ICAM-2 promoter identified Sp1, GATA, and Ets (Erg) binding sites as critical for endothelial-specific expression, establishing the transcriptional basis for constitutive ICAM-2 expression on vascular endothelium.\",\n      \"evidence\": \"Reporter gene assays, site-directed mutagenesis of promoter, EMSA with endothelial nuclear extracts\",\n      \"pmids\": [\"9565596\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Chromatin-level regulation (histone marks, accessibility) not addressed\", \"Whether the same elements drive expression in non-endothelial lineages unknown\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"TNF-α and IL-1β were shown to transcriptionally down-regulate ICAM-2 via reduction of Erg binding to promoter Ets sites, explaining how inflammation reciprocally regulates ICAM-1 (up) and ICAM-2 (down) on endothelium; separately, ICAM-2-deficient mice revealed a non-redundant role in eosinophil transmigration and megakaryopoiesis.\",\n      \"evidence\": \"Promoter mutagenesis, EMSA, Erg protein levels by Western blot; ICAM-2-KO mice with allergic lung inflammation model and bone marrow chimeras\",\n      \"pmids\": [\"10574717\", \"10223354\", \"10023766\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of Erg downregulation by TNF-α not elucidated\", \"Megakaryopoiesis phenotype not mechanistically dissected\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"ICAM-2 was found to activate the PI3K/AKT survival pathway through ezrin phosphorylation, protecting B cells from apoptosis and establishing ICAM-2 as a signaling receptor, not merely a passive ligand; notably, ICAM-2 does not activate RhoA, distinguishing its signaling from ICAM-1.\",\n      \"evidence\": \"ICAM-2 clustering, phosphorylation cascades (ezrin/AKT/BAD/GSK3/FKHR), apoptosis protection assays; RhoA activity assays comparing ICAM-1 and ICAM-2 cross-linking\",\n      \"pmids\": [\"11825565\", \"12097408\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct kinase linking ezrin phosphorylation to PI3K recruitment unknown\", \"Whether AKT signaling is relevant in endothelial context not shown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Genetic deletion demonstrated that endothelial ICAM-2 promotes angiogenesis through Rac-1 activation, supporting tube formation, migration, and cell survival — establishing a vascular morphogenesis function beyond leukocyte adhesion.\",\n      \"evidence\": \"ICAM-2-deficient mice and endothelial cells, in vitro and in vivo angiogenesis models, Rac GTPase activity assays\",\n      \"pmids\": [\"15920013\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Upstream activator of Rac-1 downstream of ICAM-2 not identified\", \"Whether homophilic ICAM-2 interaction is direct or indirect unclear\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"DC-SIGN was identified as a glycan-dependent receptor for ICAM-2 via Lewis Y epitopes, establishing ICAM-2 as a scaffold for dendritic cell rolling on endothelium; separately, ICAM-2 expression was shown to suppress neuroblastoma metastasis through α-actinin-mediated actin reorganization.\",\n      \"evidence\": \"DC-SIGN binding assays with glycosylation mutants, FUT1 siRNA, rolling assays under flow; co-IP and competitive peptide assays with in vivo metastasis model\",\n      \"pmids\": [\"18155766\", \"18978946\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Lewis Y glycosylation of ICAM-2 varies by vascular bed in vivo unknown\", \"Metastasis suppression mechanism beyond actin reorganization not defined\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Systematic genetic dissection using single and double ICAM-1/ICAM-2 knockouts under physiological flow revealed that ICAM-2 specifically mediates leukocyte crawling and diapedesis (but not arrest) at the blood-brain barrier, acting sequentially with ICAM-1, JAM-A, and PECAM-1.\",\n      \"evidence\": \"Live imaging under flow with WT, ICAM-1-KO, ICAM-2-KO, and double-KO primary brain endothelial cells; intravital imaging in KO mice\",\n      \"pmids\": [\"20861356\", \"19211506\", \"24259506\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether ICAM-2 signals to endothelial cells during crawling or only serves as a passive track unknown\", \"Contribution at non-CNS vascular beds less well dissected\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"ICAM-2 was shown to regulate vascular barrier function through its cytoplasmic ERM-binding domain, activating Rac-1 to maintain N-cadherin junctions; deficiency increased thrombin-induced permeability in vivo, unifying its Rac-1 signaling role across angiogenesis and barrier maintenance.\",\n      \"evidence\": \"ICAM-2 domain mutants (ΔERM, ΔTAIL), constitutively active Rac-1 rescue, transendothelial resistance, intravital albumin extravasation in ICAM-2-KO mice\",\n      \"pmids\": [\"24593809\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"GEF linking ICAM-2/ERM to Rac-1 activation not identified\", \"Relationship between barrier and angiogenesis phenotypes not integrated\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"METTL3-mediated m6A methylation of ICAM2 mRNA was identified as an epitranscriptomic regulatory mechanism, with ICAM-2 promoting RA fibroblast-like synoviocyte pathology through PI3K/AKT/p300 in a positive feedback loop.\",\n      \"evidence\": \"MeRIP, ChIP for p300 at METTL3 promoter, siRNA and overexpression, CIA mouse model\",\n      \"pmids\": [\"36536495\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"m6A regulation of ICAM2 not confirmed in endothelial or immune cell contexts\", \"Whether m6A modification affects ICAM-2 protein level versus translation efficiency not resolved\", \"Single-lab finding\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions include: the identity of the GEF linking ICAM-2/ERM to Rac-1; whether ICAM-2 homophilic interactions are direct; the structural basis of the full radixin FERM–ICAM-2 cytoplasmic tail complex; and the physiological significance of differential glycosylation of ICAM-2 across cell types.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No co-crystal structure of ICAM-2 with LFA-1 or radixin FERM domain\", \"GEF for ICAM-2-dependent Rac-1 activation unknown\", \"In vivo relevance of differential glycosylation across vascular beds not tested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [0, 1, 2, 12, 22, 24]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [6, 7, 9, 20]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [0, 1, 2, 18]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1, 6, 8, 26]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [9, 20]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 1, 22, 23, 24, 25, 26]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [9, 11, 20, 31]},\n      {\"term_id\": \"R-HSA-1500931\", \"supporting_discovery_ids\": [0, 1, 22, 24, 26]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [9, 31]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"ITGAL\",\n      \"ITGAM\",\n      \"EZR\",\n      \"RDX\",\n      \"MSN\",\n      \"ACTN1\",\n      \"CD209\",\n      \"ICAM1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}