4-1BB Promotes the Survival of CD8+ T Lymphocytes by Increasing Expression of Bcl-xL and Bfl-1

Abstract 4-1BB, a T cell costimulatory receptor, prolongs CD8+ T cell survival. In these studies, 4-1BB stimulation was shown to increase expression of the antiapoptotic genes bcl-xL and bfl-1 via 4-1BB-mediated NF-κB activation. This signaling pathway was specifically inhibited by PDTC and was different from the pathways that enhanced CD8+ T cell proliferation. The results suggest a role for the antiapoptotic activities of Bcl-xL and Bfl-1 proteins in 4-1BB-mediated CD8+ T cell survival in vivo.