CLEVER-1 and lymphocyte trafficking. CLEVER-1 is expressed by activated blood endothelial cells, afferent lymphatic endothelium, high endothelial venules (HEVs), sinusoid endothelium, and efferent lymphatic endothelium, supporting lymphocyte adhesion and transmigration. Thus, CLEVER-1 may have an impact on all lymphocyte trafficking steps.