Early CD8 T-cell memory precursors and terminal effectors exhibit equipotent in vivo degranulation.
Bottom Line: 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 data provide direct in vivo evidence that memory-fated cells pass through a robust effector phase.
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.
No MeSH data available.
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Mentions: The data presented in Figures 2 and 3 demonstrate that FACS purified in vivo stained KLRG-1int and KLRG-1hi antigen-specific CD8 T cells from the spleen possess diverse fates despite elaborating similar degranulation in response to antigenic stimulation in the spleen. Based on (i) the increased prevalence of KLRG-1int cells in the lymph nodes (Figure 1 and Supplementary Figures 1 and 2) at all time-points post-infection; (ii) the preferential localization of the KLRG-1int donors in the lymph nodes rather than the KLRG-1hi donor cells shortly after the adoptive transfer into infection-matched recipients;9 and (iii) previous reports that lymph node-derived effector CD8 T cells enter the memory pool more readily than spleen derived effectors,24 we next compared the in vivo degranulation of the MPECs and SLECs in lymph nodes and in peripheral sites, such as the liver. As observed in splenocytes (Figure 3), the day 4.75 effectors degranulated more than the day 8 effectors in all other tissue sites analyzed as well (Figure 4). Moreover, the degranulation readouts were largely similar at the 1 and 2 h assay times, as observed previously (Figure 3), indicating rapid degranulation after stimulation. Surprisingly, we found an evident difference in the level of effector cell degranulation in the lymphoid tissues compared to the non-lymphoid tissues (Figure 4). Both the day 4.75 and 8 effectors exhibited more degranulation in the liver than in the lymph nodes. In general, the viral loads in the inguinal lymph nodes were approximately 10-fold lower than in the liver after intraperitoneal acute infection with LCMV at approximately day 4.5 after infection, and all of the tissues were largely cleared of plaqueable virus at day 8 after infection (Figure 4b). These data are consistent with the measurable differences in the in vivo antigenic encounters and degranulation between day 4.5 and day 8 after infection as well as the lesser degree of degranulation observed in the inguinal lymph node.
No MeSH data available.