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IL-1, generally considered an amplifier of adaptive immune responses, has been proposed for use as adjuvant during immunization with weak immunogens. However, its effects on memory T cell function remain largely undefined. Using the murine model of acute viral infection, in this paper, we show that in addition to augmenting the size of the Ag-specific pool, IL-1 signals act directly on CD8 T cells to promote the quality of effector and memory responses. Ablation of IL-1R1 or MyD88 signaling in T cells led to functional impairment; both the ability to produce multiple cytokines on a per cell basis (polyfunctionality) and the potential for recall proliferation in response to antigenic restimulation were compromised. IL-1 supplementation during priming augmented the expansion of Ag-specific CD8 T cells through the MyD88-IRAK1/4 axis, resulting in a larger memory pool capable of robust secondary expansion in response to rechallange. Together, these findings demonstrate a critical role of the IL-1-MyD88 axis in programming the quantity and quality of memory CD8 T cell responses and support the notion that IL-1 supplementation may be exploited to enhance adoptive T cell therapies against cancers and chronic infections. [ABSTRACT FROM AUTHOR]

Early after priming, effector CD8 T cells are distinguished into memory precursor and short-lived effector cell subsets (MPECs and SLECs). Here, we delineated a distinct in vivo heterogeneity in killer cell lectin-like receptor G1 (KLRG-1) expression, which was strongly associated with diverse MPEC and SLEC fates. These in vivo MPECs and SLECs expressed equivalent levels of cytotoxic molecules and effector cytokines. Using a unique in vivo degranulation assay, we found that the MPECs and SLECs similarly encountered infected target cells and elaborated equivalent levels of cytotoxicity in vivo. These data provide direct in vivo evidence that memory-fated cells pass through a robust effector phase. Additionally, the preferential localization of the MPECs in the lymph nodes, where a lesser degree of cytotoxicity was elaborated, suggests that the MPECs may be protected from excessive stimulation and terminal differentiation by virtue of their differential tissue localization. These data provide novel mechanistic insights into the linear decreasing potential model of memory differentiation.