DX5 antigen has been recently characterized as CD49b. It is a 150 kD integrin alpha chain also known as alpha2 integrin, VLA-2 alpha chain, and integrin alpha2 chain. CD49b non-covalently associates with CD29 (beta1 integrin) to form the CD49b/CD29 complex known as VLA-2, a receptor for collagen and laminin. CD49b is expressed on platelets, the majority of NK cells, NKT cells, and a small subset of CD8+ T cells (this population can be significantly increased following viral infection). DX5 is used for the identification and isolation of NK cells, and is especially useful for identifying NK cells in mice lacking the NK1.1 antigen.