CD49b is a 170 kD transmembrane protein, also known as α2 integrin, VLA-2 α chain, Integrin α2 and GPIa. It associates with CD29 (β1 integrin) to form VLA-2, a collagen and laminin receptor on many cell types including monocytes, platelets, activated T cells, megakaryocytes, neuronal cells, epithelial cells, and osteoclasts. CD49b has been reported to interact with F-actin and matrix metalloproteinase 1. CD49b is a platelet alloantigen and has been associated with neonatal alloimmune thrombocytopenia. Deficiencies in this protein have been associated with hemorrhagic disorders.