Integrin alpha 2b (CD41) is a calcium-dependent, noncovalently associated heterodimer and contains a heavy chain (GPIIb alpha) and a light chain (GPIIb beta) linked by a single disulfide bond. The Integrin alpha 2B chain interacts with the Integrin beta 3 subunit/CD61 to form the platelet glycoprotein complex, gpIIb/IIIa. It is expressed on platelets and megakaryocytes. Ligands for the gpIIb/IIIa heterodimer include fibrinogen, von Willebrand factor, fibronectin, vitronectin, and thrombospondin. The gpIIb/IIIa complex is the major Integrin on platelets and is important for platelet adhesion and aggregation.