CD42a Antigen

The CD42a antigen (GPIX) is a single-chain transmembrane glycoprotein of 22 kDa that forms a noncovalent complex with CD42b, CD42c and CD42d (GPIbα, GPIbβ, and GPV). The CD42a expression is restricted to platelets and megakaryocytes. The GPIb-IX-V complex is the platelet receptor for von Willebrand factor and is known as von Willebrand's factor-dependent adhesion receptor. Although GPIb-IX-V primarily functions as a platelet receptor for von Willebrand factor (VWF), it can also bind to other ligands present in circulation such as thrombin, P-selectin, integrin αMβ2, factor XI, factor XII, high- molecular-weight kininogen, as well as a number of snake venom proteins.