N-terminal immunoglobulin domain of the intercellular adhesion molecules ICAM-1 (Cluster of Differentiation 54 or CD54), ICAM-2 (CD102) and ICAM-3 (CD50); members of the I-set of IgSF domains
The members here are composed of the immunoglobulin (Ig) domain found in the N-terminus of the intercellular adhesion molecules ICAM-1 (Cluster of Differentiation 54 or CD54), ICAM-2 (CD102), and ICAM-3 (CD50). ICAM-1, ICAM-2, and ICAM-3 mediate a variety of critical intercellular adhesion events in the immune system through interactions with their counter-receptors, the beta2-integrins LFA-1 (CD11a/CD18), Mac-1 (CD11b/CD18), p150,95 (CD11c/CD18), and CD11d/CD18. The ICAMs are type I transmembrane glycoproteins belonging to the immunoglobulin superfamily (IgSF). The binding of the ICAM family members with the beta2-integrins physically stabilizes interactions between pairs of T and B cells, T cells and antigen-presenting cells (APCs), and brings effector cells such as cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells into close proximity to their target cells. All three ICAMs share a common polypeptide homology and structural motif, and the ability to bind LFA-1. The distinct functional role of each ICAM is affected by their relative affinities for LFA-1 (ICAM-1 > ICAM-2 > ICAM-3). ICAM-1 is expressed in most tissues at low levels, and expression is increased by inflammatory cytokines. In contrast, ICAM-2 is expressed predominantly on endothelium and leukocytes (except neutrophils), and its expression generally is not responsive to cytokines. ICAM-3 is expressed on leukocytes and Langerhans cells, but not on resting, cytokine-induced endothelium, or nonhematopoietic tissues.
Jiyao W et al.(2023). "The conserved domain database in 2023.",