CD43 is a 95-135 kD type I transmembrane glycoprotein known as leukosialin, leukocyte sialoglycoprotein, sialophorin, and galactoglyprotein. It is expressed at high levels on the surface of all leukocytes (except on resting B cells) and at low levels on platelets, negative on erythrocytes. The expression of CD43 on T cells and neutrophils is rapidly downregulated by proteolytic shedding after activation with various stimuli. The soluble form of CD43 is present in human serum. It has been reported that CD43 plays a role in anti-adhesive functions, but also mediates adhesion via its interaction with CD54 or some lectins. Similarly, CD43 is implicated in anti-apoptotic and proapoptotic signaling.