Regulatory T cells limit unconventional memory to preserve the capacity to mount protective CD8 memory responses to pathogens.

Da Costa, Andreia S; Graham, Jessica B; Swarts, Jessica L; Lund, Jennifer M · Proc Natl Acad Sci U S A · 2019

basic_science · Level V

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Abstract

Immunological memory exists so that following infection an expanded population of pathogen-specific lymphocytes can rapidly and efficiently control infection in the case of reexposure. However, in the case of CD8+ T lymphocytes, a population of unconventional CD44+CD122+ virtual memory T cells (T<sub>VM</sub>) has been described that possesses many, though not all, features of "true memory" T cells, without the requirement of first encountering cognate antigen. Here, we demonstrate a role for regulatory T cell-mediated restraint of T<sub>VM</sub> at least in part through limiting IL-15 <i>trans</i>-presentation by CD11b+ dendritic cells. Further, we show that keeping T<sub>VM</sub> in check ensures development of functional, antigen-specific "true" memory phenotype CD8+ T cells that can assist in pathogen control upon reexposure.

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