The beta 7 integrins in mucosal homing and retention

Lymphocytes recirculate extensively throughout the body and then localize in tissues and lymphoid organs. This is accomplished by an array of adhesion molecules on lymphocytes and counter-receptors on the vascular endothelium, extracellular matrix and the epithelium. Recent studies have identified several of the specific molecular interactions that mediate lymphocyte trafficking. Lymphocytes expressing alpha 4 beta 7 home to the intestine through recognition of the mucosal addressin cell adhesion molecule-1 (MAdCAM-1) expressed on Peyer's patch high endothelial venules. T cells in nearly all mucosal epithelial sites express the alpha E beta 7 integrin which has been shown to mediate lymphocyte binding to epithelial cell E-cadherin. Thus, members of the B7 subfamily of integrins, alpha E beta 7 and alpha 4 beta 7, and their counter-receptors, are believed to play key roles in directing lymphocyte traffic to and retention in mucosal organs.