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

The integrins α 4 β 7 and α 4 β 1 mediate adhesion to the mucosal addressin cell adhesion molecule‐1 (MAdCAM‐1) and the vascular cell adhesion molecule‐1 (VCAM‐1) and are important in T cell and allergic inflammatory reactions in the rat. The relative contributions of α 4 β 7 and α 4 β 1 in these reactions is unknown. To examine the role of α 4 β 7 in the rat a new mAb, TA‐6, was developed. TA‐6 inhibited adhesion to MAdCAM‐1 but not to VCAM‐1, a characteristic of α 4 β 7 adhesion, and immunofluorescence and immunoprecipitation studies were compatible with binding to α 4 β 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 adhesion to peripheral lymph nodes and T cell migration to peripheral lymphoid tissues or cutaneous inflammatory sites, and was not expressed on connective tissue mast cells. J. Leukoc. Biol. 65: 649–657; 1999.