CD49e is a type I integral membrane glycoprotein, known as alpha5 integrin, VLA-5 alpha chain. It forms noncovalent heterodimer with integrin beta1 (CD29). CD49e contains two disulfide-linked subunits of 135 kD and 24 kD, and is mainly expressed on thymocytes, activated lymphocytes, endothelial cells, osteoblasts, melanoma, and some myeloid leukemia cells. CD49e/CD29 complex binds to fibronection and neural adhesion molecule L1. It mediates monocytes migration, involves in the regulation of cells survival and apoptosis, and co-stimulates T cell activation.