Diet-induced obesity does not impact the generation and maintenance of primary memory CD8 T cells

The extent to which obesity compromises the differentiation and maintenance of protective memory CD8 T cell responses and renders obese individuals susceptible to infection remains unknown. In this study, we show that diet-induced obesity did not impact the maintenance of pre-existing memory CD8 T cells, including acquisition of a long-term memory phenotype (i.e., CD27(hi), CD62L(hi), KLRG1(lo)) and function (i.e., cytokine production, secondary expansion, and memory CD8 T cell-mediated protection). Additionally, obesity did not influence the differentiation and maintenance of newly evoked memory CD8 T cell responses in inbred and outbred hosts generated in response to different types of systemic (LCMV, L. monocytogenes) and/or localized (influenza virus) infections. Interestingly, the rate of naive-to-memory CD8 T cell differentiation after a peptide-coated dendritic cell immunization was similar in lean and obese hosts, suggesting that obesity-associated inflammation, unlike pathogen- or adjuvant-induced inflammation, did not influence the development of endogenous memory CD8 T cell responses. Therefore, our studies reveal that the obese environment does not influence the development or maintenance of memory CD8 T cell responses that are either primed before or after obesity is established, a surprising notion with important implications for future studies aiming to elucidate the role obesity plays in host susceptibility to infections.