Cutting edge: Stimulation of CD28 with B7-2 promotes focal adhesion-like cell contacts where Rho family small G proteins accumulate in T cells

Unless a costimulatory signal is provided, TCR recognition of Ag bound to the MHC is insufficient to induce optimal T cell proliferation or the production of IL-2, Here we show that the stimulation of CD28, a T cell costimulatory receptor, by a specific Ab increases F-actin contents in T cells, The interaction between T cells and B7-2-transfected Chinese hamster ovary cells expressing the CD28 ligand leads to the rearrangement of the actin cytoskelton in the region of cell-cell contact, Within the Rho family of G proteins, Rac1, but not Rho, translocates to the sites of cell-cell contact where Tailin also accumulates, These results indicate that the interaction between B7-2 and CD28 establishes a focal adhesion-like cell contact between T cell and APCs. The results also suggest that CD28 signaling is primarily transduced by a cytoskeletal rearrangment/signaling pathway mediated by the Rho family G proteins.