CD28 Costimulation Can Promote T Cell Survival by Enhancing the Expression of Bcl-x(L)

摘要

T cell activation through thr TCR can result in either cell proliferation or celldeath. The role of co-stimulatory receptors in regulating T cell survival has not been defined. Here, we present data demonstrating that CD28 co-stimulation enhances the in vitro survival of activated T cells. One mechanism for this enhancement is the ability of CD28 costimulation to augment the production of 1L-2, which acts as an extrinsic survival factor for T cells. In addition, CD28 co-stimulation augments the intrinsic ability of T cells to resist apoptosis. Although CD28 signal transduction had no effect on Bcl-2 expression of Bcl-Xl substantially. Transfection experiments demonstrated that this level of Bcl-Xl could prevent T cell death in response to TCR cross-linking, Fas cross-linking, or lL-2 withdrawal. These data suggest that an important role of CD28 co-stmulation is to augment T cell survival during antigen activation.