Selective antibody blockade of lymphocyte migration to mucosal sites and mast cell adhesion

The integrins alpha(4)beta(7) and alpha(4)beta(1) mediate adhesion to the m ucosal addressin cell adhesion molecule-1 (MAdCAM-1) and the vascular cell adhesion molecule-1 (VCAM-1) and are important in T cell and allergic infla mmatory reactions in the rat. The relative contributions of alpha(4)beta(7) and alpha(4)beta(1) in these reactions is unknown. To examine the role of alpha(4)beta(7) in the rat a new mAb, TA-6, was developed. TA-6 inhibited a dhesion to MAdCAM-1 but not to VCAM-1, a characteristic of alpha(4)beta(7) adhesion, and immunofluorescence and immunoprecipitation studies were compa tible with binding to alpha(4)beta(7). TA-6 blocked rat lymphocyte adhesion to mesenteric lymph nodes and T cell migration to mucosal lymphoid tissues and it bound to rat mucosal mast cells. TA-6 did not inhibit lymphocyte ad hesion to peripheral lymph nodes and T cell migration to peripheral lymphoi d tissues or cutaneous inflammatory sites, and was not expressed on connect ive tissue mast cells.