Regulation of integrin activation through the B-cell receptor.

Effective immune surveillance is absolutely dependent on the migration of lymphocytes throughout the body and on their successful recognition of specific antigens. Both of these functions rely on the capacity of integrins that are expressed on the surface of lymphocytes to respond in a highly regulated manner to a variety of chemokines and antigens. This Commentary is primarily concerned with the role of the B-cell integrins LFA-1 and VLA-4 in the antigen-recognition process, and summarises what is currently known about the molecular mechanisms of ;inside-out' integrin activation in response to B-cell-receptor stimulation. Recent investigations have identified Vav, PI3K and small GTPases as crucial regulators of the inside-out activation of B-cell integrins. These observations are of particular interest as they allude to an underlying mechanism by which B-cell-receptor-mediated signalling is linked to cytoskeleton reorganisation and subsequent integrin activation.