Cognate CD4+ T cells enhance CTL survival and memory programming via IL-2, CD40L and acquired pMHC-I signaling (46.16)

Abstract

Abstract A hallmark of cellular immunity is the generation of memory CD8+ cytotoxic T lymphocytes (CTL) that escape activation-induced cell death (AICD) during the effector phase. Factors governing effector CTL survival in CD4+ T helper1 cells (Th1) that lead to functional memories are poorly understood. Here, we determined the role of Th1 cells with acquired antigen-presenting machineries on effector CTL fates. Contrary to previously known immune-regulatory mechanisms among Th1 or CTL interactions, our study establishes a novel co-operative role of cognate Th1-CTL interactions. Th1’s help mediated enhanced CTL survival, and functional memory CTL development, capable of protecting against lethal tumor challenge, via CD40L, IL-2, and acquired peptide-MHC-I signaling. Helped CTL showed survival advantages by displaying mRNA profiles similar to naïve CD8+ T cells, and increased NF-kB and Akt1 activation. In contrast, unhelped CTL underwent rapid AICD-mediated contraction through increased NFATc1 activation, and up-regulation of pro-apoptotic and down-regulation of anti-apoptotic genes known to mediate FasL- and Trail-associated apoptotic pathways. This form of Th1-CTL cooperation could explain why memory CTL generated under cognate Th1’s help show survival and recall advantages, a phenomenon frequently observed in organ transplantations, cancers, and many autoimmune and infectious diseases, and may impact effective adoptive CTL therapy of cancers.