Functional and genomic profiling of effector CD8 T cell subsets with distinct memory fates

Abstract

An important question in memory development is understanding the differences between effector CD8 T cells that die versus effector cells that survive and give rise to memory cells. In this study, we provide a comprehensive phenotypic, functional, and genomic profiling of terminal effectors and memory precursors. Using killer cell lectin-like receptor G1 as a marker to distinguish these effector subsets, we found that despite their diverse cell fates, both subsets possessed remarkably similar gene expression profiles and functioned as equally potent killer cells. However, only the memory precursors were capable of making interleukin (IL) 2, thus defining a novel effector cell that was cytotoxic, expressed granzyme B, and produced inflammatory cytokines in addition to IL-2. This effector population then differentiated into long-lived protective memory T cells capable of self-renewal and rapid recall responses. Experiments to understand the signals that regulate the generation of terminal effectors versus memory precursors showed that cells that continued to receive antigenic stimulation during the later stages of infection were more likely to become terminal effectors. Importantly, curtailing antigenic stimulation toward the tail end of the acute infection enhanced the generation of memory cells. These studies support the decreasing potential model of memory differentiation and show that the duration of antigenic stimulation is a critical regulator of memory formation.

Bim controls IL-15 availability and limits engagement of multiple BH3-only proteins

“…Although suggested in a prior study, transfers of purified populations of effector subsets were not performed making it difficult to determine whether conversion had occurred. 12 However, in other work, transferred WT KLRG1 hi cells did not revert to KLRG1 lo cells; 1,41,42 and here the numbers of KLRG1 lo CD127 hi cells in Bim À / À mice did not increase in proportion to the loss of KLRG1 hi C-D127 lo cells, arguing against conversion. More work is needed to determine if, in the absence of death, some KLRG1 hi CD127 lo cells convert to KLRG1 lo CD127 hi cells.…”

Effector CD8 T cells dedifferentiate into long-lived memory cells

“…Effector and memory antigen-specific CD8 T cells were identified and purified by Fluorescence Activated Cell Sorting (FACS) using H-2D b tetramers bound to LCMV peptide GP33-41 conjugated to a fluorophore, along with CD8, CD44, CD127, Klrg1 and CD62L-fluorophore conjugated antibodies as previously described. 11,14,25,26 . To generate LCMV-specific CD8 T cell chimeras, transgenic P14 CD8 T cells with an engineered TCR that recognize the epitope GP33-41 of LCMV were harvested from naïve P14 TCR transgenic mice and adoptively transferred intravenously to C57BL/6 mice (cell# / mouse is specified in the figure legend) 11,27–29 .…”

“…11,14,25,26 . To generate LCMV-specific CD8 T cell chimeras, transgenic P14 CD8 T cells with an engineered TCR that recognize the epitope GP33-41 of LCMV were harvested from naïve P14 TCR transgenic mice and adoptively transferred intravenously to C57BL/6 mice (cell# / mouse is specified in the figure legend) 11,27–29 . Congenically marked LCMV-specific CD8 T cells were sorted using fluorescently labeled CD90.1 (Thy1.1) and CD8 antibodies as previously described 14 .…”

The (gradual) rise of memory inflation

“…The functions in vivo are not yet well explored but it might be they perform some similar “tuning” activity eg, in preventing overstimulation and promoting long‐term survival. Expression of KLRG1—which has well‐documented inhibitory functions—is often used as a marker for this type of cell population 60, 62. In contrast, NKG2D is stimulatory, so the balance between signaling through such receptors may be critical for activation as it is in NK cells.…”