ICAM1 and atherosclerosis: The initial step in atherosclerosis is the adhesion of leukocytes to activated endothelial cells mediated by intracellular adhesion molecule-1 (ICAM-1).2 Soluble ICAM-1 (sICAM-1) is a circulating form of ICAM-1 and has been shown to reflect cell surface expression of ICAM-1 in human vascular endothelial cells.