The AK-4 monoclonal antibody specifically reacts with human CD62P (P-Selectin), a 140 kDA type I transmembrane glycoprotein also known as platelet activation-dependent granule membrane protein (PADGEM). Upon activation it is quickly transported to the plasma membrane from the alpha-granules of platelets and WEibel-Palade bodies of endothelial cells. It is essential to the functions of cell adhesion during inflammatory reactions and in the interaction of platelets with monocytes and neutrophils.