Interest of circulating ICAM-1 plasma levels: From physiology to clinical applications.

Intercellular adhesion molecule 1 (ICAM-1) is an adhesion-related molecule belonging to the immunoglobulin superfamily. This molecule is found on the cell membrane of endothelial cells. When activated ICAM-1 allows stable leu kocyte adhesion to the endothelial surface. ICAM-1 is found not only in the membrane form but also circulating in serum. ICAM-1s probably results from proteolytic cleavage of membrane ICAM-1 (extracellular part of ICAM-1). Th is enables ICAM-1s to bind leukocyte integrin receptors such as LFA-1 (CD11 a/CD18) and Mac-1 (CD11b/CD18) and therefore provide adaptive changes in th e adhesion process between circulating cells and the endothelium. ICAM-1 was first detected in sera of healthy subjects. It is currently poss ible to assay ICAM-1 in serum, CSF and bronchoalveolar lavage fluid as well as in cell culture supernatants. ICAM-1s levels are increased in many pathological states, mainly immune dis orders, inflammation and cancer. Such high levels of plasma ICAM-1s may be of interest in for diagnostic and prognostic purposes.