Transcriptional basis of CD4 T cel help for memory CD8 T cell formation

CD4+ T-cell help is required for the generation of CD8+ cytotoxic T lymphocyte (CTL) memory. We here reveal how “help” signals delivered during priming impact memory differentiation of CTLs, as informed by genome-wide analyses. “Help” signals promoted the IL-15-dependent maintenance of central memory (TCM) cells. However, they had a much larger impact on the generation of effector memory (TEM) cells and their gene expression program . CD4+ T-cell help created TEM cells that produced Granzyme B and IFNg after antigen-independent recall with IL-12 and IL-18. Furthermore, “helped” memory CTLs expressed the effector program characteristic of “helped” primary CTLs upon recall with MHC class I-restricted antigen only, due to both epigenetic imprinting and sustained mRNA expression of relevant genes . Thus, CD4+ T-cell help delivered during priming creates CD8+ TEM cells with innate and help-independent recall capacities. Whole transcriptome analysis of effector and central memory CD8 T cells primed in the presence or absence of CD4 T cell help.