Pathogen-Induced Inflammatory Environment Controls Effector and Memory CD8+ T Cell Differentiation

<jats:title>Abstract</jats:title> <jats:p>In response to infection, CD8+ T cells integrate multiple signals and undergo an exponential increase in cell numbers. Simultaneously, a dynamic differentiation process occurs, resulting in the formation of short-lived effector cells (SLECs; CD127lowKLRG1high) and memory precursor effector cells (CD127highKLRG1low) from an early effector cell that is CD127lowKLRG1low in phenotype. CD8+ T cell differentiation during vesicular stomatitis virus infection differed significantly than during Listeria monocytogenes infection with a substantial reduction in early effector cell differentiation into SLECs. SLEC generation was dependent on Ebi3 expression. Furthermore, SLEC differentiation during vesicular stomatitis virus infection was enhanced by administration of CpG-DNA, through an IL-12–dependent mechanism. Moreover, CpG-DNA treatment enhanced effector CD8+ T cell functionality and memory subset distribution, but in an IL-12–independent manner. Population dynamics were dramatically different during secondary CD8+ T cell responses, with a much greater accumulation of SLECs and the appearance of a significant number of CD127highKLRG1high memory cells, both of which were intrinsic to the memory CD8+ T cell. These subsets persisted for several months but were less effective in recall than memory precursor effector cells. Thus, our data shed light on how varying the context of T cell priming alters downstream effector and memory CD8+ T cell differentiation.</jats:p>