Clone 2C9.G2 (HMβ3-1) recognizes a 110 kDa integrin β chain known as CD61 or Integrin β3. Owing to multiple α/β subunit combinations, integrins form an array of heterodimeric receptors, each recognising a multitude of ligands. CD61, in association with either αv (CD51) or αIIb (CD41) integrin, binds to fibrinogen, fibronectin, von Willebrand factor, prothrombin, disintegrins and thrombospondin. Due to binding to various extracellular matrix proteins and cellular receptors, integrins play a significant role in cell adhesion and cell movement. Furthermore, a pro-apoptotic function of CD61 has been suggested using a hepatocellular carcinoma (HCC) cell line and patient tissues. Expression of CD61 is found on platelets, B cell subsets, myeloid cells, mast cells, osteoclasts, endothelium, megakaryocytes, and smooth muscle cells.