The HMa2 antibody reacts with mouse CD49b, a 150 kDa glycoprotein member of the integrin αfamily. CD49b, also known as integrin αalpha2, associates non-covalently with CD29 (integrin αbeta1) to form the VLA-2 heterodimer. VLA-2 integrin αs function as cellular receptors for collagen and laminin. CD49b is expressed by platelets, intestinal epithelial cells, NK cells, epithelial cells, and a subset of CD4+ T cells. CD49b plays an essential role in mediating the adhesion of cells to the extracellular matrix.