Recognizes an 85-115kDa protein (variation with cell type), identified as intercellular adhesion molecule (ICAM-1) (Workshop IV). It has 7 potential N-linked glycosylation sites. ICAM-1 is a single chain glycoprotein of Ig supergene family, present on unstimulated endothelial cells (EC) and on a variety of other cell types including activated fibroblasts, EC, macrophages, and lymphocytes. ICAM-1 mediates cell adhesion by binding to integrins CD11a/CD18 (leukocyte adhesion molecule, LFA-1) and to CD11b/CD18 (Mac-1). This interaction enhances antigen-specific T-cell activation. ICAM-1 also binds to CD43 and to Plasmodium falciparum infected RBCs. W-CAM-1 MAb blocks aggregation of cell lines mediated by the ICAM-1 and blocks homotypic binding of purified populations of activated T- and B-lymphocytes and also aggregation of mixed T- and B-cell blasts. It inhibits T-cell adhesion to normal human endothelial cells. Activation induced by cell-cell contact (mixed lymphocyte reaction, T-cell mediated B-cell activation) is significantly inhibited. This MAb blocks elements of both effector arms of immune system (cytotoxic cell function and Ig production).