Integrin alpha 4 beta 7 co-stimulation of human peripheral blood T cell proliferation.

The integrin alpha 4 beta 7 mediates lymphocytes adhesion to VCAM-1 on activated endothelium, fibronectin in the extracellular matrix, and the mucosal vascular addressin MAdCAM-1. It is unclear whether alpha 4 beta 7 performs any function beyond directing specific adhesion reactions. We addressed the possibility that triggering of alpha 4 beta 7 with a specific monoclonal antibody was capable of delivering an accessory stimulus that would coactivate T cells and lead to proliferation. At submitogenic levels of anti-CD3 stimulation, triggering of alpha 4 beta 7 by immobilized mAb ACT-1 resulted in T cell blastogenesis, IL-2 production, expression of the IL-2 receptor alpha chain CD25, and ultimately DNA synthesis. These results indicate that the integrin alpha 4 beta 7 is involved in more than lymphocyte adhesion and homing but also plays a role in cell signaling.