Accumulation of T Lymphocytes at Mucosal Sites

T lymphocyte migration serves to bring the entire range of T lymphocyte receptor specificities in contact with antigen. It also serves to disseminate the products of an immune response, effector cells and memory cells, to 

A recent conceptual development has been that adhesion and extravasation of T lymphocytes, and leucocytes in general, occurs through several sequential steps (Butcher, 1991 Lawrence and Springer, 1991 Shimizu et al., 1992). 

A transendothelial migration step following firm adhesion. 

In contrast to naive T lymphocytes, memory T lymphocytes migrate non-randomly in a partially tissue-specific fashion (Salmi et til., 1992), suggesting that the mucosal environment in which T lymphocyte activation occurs may imprint a pattern of selectivity on the activated cell. The selective migration of a subset of T lymphocytes through the gut is probably the best characterized example of tissue-specific homing (Mackay, 

Gut-tropic cells in humans express the o4/87 inte-grin, which is a counter-receptor for the mucosal vascular addressin MadCam-1 expressed on high endothelial venules of Peyer s patches and mesenteric lymph nodes, and on the endothelium of the gut mucosa (Briskin etal., 

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