CD51 is a 140 kD protein, also known as alphaV integrin, vitronectin receptor, and integrin alphaV. It is a member of the integrin family, expressed on activated T cells, polymorphonuclear granulocytes, platelets, blastocysts, and osteoclasts. CD51 forms heterodimers by association with integrins beta1, beta3, beta5 or beta6; these complexes then act as receptors for multiple extracellular matrix proteins (ECM). The alphav integrin heterodimers have varied functions in development, stimulation/activation and homeostasis. The primary ligands for CD51 complexes are fibronectin, fibrinogen, vitronectin, thrombspondin, von Willebrand factor, and CD31. The RMV-7 antibody has been reported to block binding of CD51 to vitronectin, fibronectin, and CD31 in some cell types, as well as blocking LAK cell cytotoxicity.