The WM59 monoclonal antibody specifically binds to platelet endothelial cell adhesion molecule-1, (PECAM-1, PECAM1), which is also known as GPIIA', or EndoCAM. CD31 is a 130 kDa type I transmembrane glycoprotein that belongs to the Ig gene superfamily. CD31 has wide tissue distribution and is expressed on platelets, monocytes, granulocytes, NK cells, T cell subsets, and in high amounts on endothelial cells. CD31 functions as a vascular endothelial cell adhesion molecule and is involved in the transendothelial migration of leucocytes in inflammatory responses. It might be involved in thrombosis, angiogenesis, and wound healing. The WM59 appears to recognize an epitope proximal to extracellular domain 2 of CD31.
Clone WM59 also cross-reacts with peripheral blood platelets and leukocytes of baboon, and both rhesus and cynomolgus macaque monkeys. The staining intensity of WM59+ platelets is similiar to that observed with peripheral blood platelets from normal human donors. Lymphocytes, monocytes, and granulocytes react less with WM59 than normal human leukocytes.