Very late lymphocyte-activation antigen

Integrins themselves are found on nearly all cells and mediate several physiological responses, such as cell-cell and cell-matrix interactions. Three families of integrins, each family with a common beta subunit in combination with distinct alpha subunits, have been recognized. The beta 1 family, also called very late lymphocyte-activation antigen or VLA, has receptors mediating extracellular matrix interactions with molecules such as collagen, laminin, and fibronectin. Naturally, platelets contain many of the receptors of the beta 1 family. 

The largest numbers of integrins are members of the (31 integrins, also known as the very late antigen (VLA) subfamily because of its late appearance after activation. There are at least seven receptors characterized from this subfamily, each with different ligand specificity. Among the most studied include the 04(31 and a5 31 receptors. The leukocyte integrin a4 31 is a cell adhesion receptor that is predominantly expressed on lymphocytes, monocytes and eosinophils. 

Nakayama, H., Sano, H., Nishimura, T., Yoshidi, S., and Iwamoto, I. (1994) Role of vascular cell adhesion molecule 1/very late activation antigen 4 and intercellular adhesion molecule 1/lymphocyte function-associated antigen 1 interactions in antigen-induced eosinophil and T cell recruitment into the tissue. J. Exp. Med. 179,1145-1154. 

The Pi integrins are also known as the very late antigen (VLA) subfamily because they were first identified on lymphocytes several days after activation.31 At present there are six members, all of which bind to proteins of the extracellular matrix (see Table 6.1). Unlike the other molecules, VLA-4 (CD49d) is found on the majority of unstimulated T lymphocytes, its expression being higher on memory than naive cells.32 It contributes to T-cell adhesion to inflamed endothelium by interacting with VCAM-1 and, as we shall see later, VLA-4 facilitates T-cell infiltration across the BBB in EAE. 

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