Early primed KLRG1- CMV-specific T cells determine the size of the inflationary T cell pool.

• Main Authors: Nicolas S Baumann, Suzanne P M Welten, Nicole Torti, Katharina Pallmer, Mariana Borsa, Isabel Barnstorf, Jennifer D Oduro, Luka Cicin-Sain, Annette Oxenius
• Format: Article
• Language: English
• Published: Public Library of Science (PLoS) 2019-05-01
• Series: PLoS Pathogens
• Online Access: https://doi.org/10.1371/journal.ppat.1007785
• ISSN: 1553-7366; 1553-7374

Memory T cell inflation is a process in which a subset of cytomegalovirus (CMV) specific CD8 T cells continuously expands mainly during latent infection and establishes a large and stable population of effector memory cells in peripheral tissues. Here we set out to identify in vivo parameters that promote and limit CD8 T cell inflation in the context of MCMV infection. We found that the inflationary T cell pool comprised mainly high avidity CD8 T cells, outcompeting lower avidity CD8 T cells. Furthermore, the size of the inflationary T cell pool was not restricted by the availability of specific tissue niches, but it was directly related to the number of virus-specific CD8 T cells that were activated during priming. In particular, the amount of early-primed KLRG1- cells and the number of inflationary cells with a central memory phenotype were a critical determinant for the overall magnitude of the inflationary T cell pool. Inflationary memory CD8 T cells provided protection from a Vaccinia virus challenge and this protection directly correlated with the size of the inflationary memory T cell pool in peripheral tissues. These results highlight the remarkable protective potential of inflationary CD8 T cells that can be harnessed for CMV-based T cell vaccine approaches.