ABSTRACT
Th e selectin family comprises three proteins designated by the prefi xes E (endothelial), P (platelets), and L (leukocyte). E-selectin and P-selectin are expressed by endothelial cells, and L-selectin is expressed only on leukocytes. E-selectin (CD62E) was initially described as an antigen that was induced in endothelium aft er stimulation by interleukin-1 (IL-1) and was involved in the adhesion of neutrophil and several leukemic cell lines. P-selectin (CD62P) is an adhesion protein that was initially characterized in platelet and was subsequently shown to be present also in endothelial cells. Th e soluble P-selectin has been detected in the plasma of normal individuals in a very small quantity (0.15 μg/mL). However, it has not been shown that this is the secreted form rather than protein shed from platelets or endothelial cells. Th is raises the possibility that soluble plasma P-selectin may prime leukocyte adhesion molecule to P-selectin expressed on endothelium (Dunlop et al. 1992, Hogg et al. 1991). L-selectin (CD62L) is found only on leukocytes. It is shown to be expressed on most other peripheral blood leukocytes and is involved in leukocyte traffi c in the systemic microcirculation.
