VLA-4 integrin concentrates at the peripheral supramolecular activation complex of the immune synapse and drives T helper 1 responses

The integrin alpha4beta1 (VLA-4) not only mediates the adhesion and transendothelial migration of leukocytes, but also provides costimulatory signals that contribute to the activation of T lymphocytes. However, the behavior of alpha4beta1 during the formation of the immune synapse is currently unknown. Here, we show that alpha4beta1 is recruited to both human and murine antigen-dependent immune synapses, when the antigen-presenting cell is a B lymphocyte or a dendritic cell, colocalizing with LFA-1 at the peripheral supramolecular activation complex. However, when conjugates are formed in the presence of anti-alpha4 antibodies, VLA-4 colocalizes with the CD3-zeta chain at the center of the synapse. In addition, antibody engagement of alpha4 integrin promotes polarization toward a T helper 1 (Th1) response in human in vitro models of CD4(+) T cell differentiation and naive T cell priming by dendritic cells. The in vivo administration of anti-alpha4 integrin antibodies also induces an immune deviation to Th1 response that dampens a Th2-driven autoimmune nephritis in Brown Norway rats. These data reveal a regulatory role of alpha4 integrins on T lymphocyte-antigen presenting cell cognate immune interactions.