Inter-Cellular Adhesion Molecule 1 (ICAM1) is a type of intercellular adhesion molecule continuously present in low concentrations in the membranes of leukocytes and endothelial cells. As an endothelial and leukocyte-associated transmembrane protein, ICAM1 is well known for its importance in stabilizing cell-cell interactions and facilitating leukocyte endothelial transmigration. The presence of heavy glycosylation and other structural characteristics lend ICAM1 binding sites for a number of immune-associated ligands. Notably, ICAM-1 binds to macrophage adhesion ligand-1 (Mac-1; ITGB2 / ITGAM), leukocyte function associated antigen-1 (LFA-1/integrin), and fibrinogen.ICAM-1 expressed by respiratory epithelial cells is also the binding site for rhinovirus, the causative agent of most common colds.