Transcriptomes and metabolism define heterogeneous mouse and human MAIT cells [mouse]

Mucosal-associated invariant T (MAIT) cells are a subpopulation of T lymphocytes that respond to microbial metabolites. We performed single-cell RNA sequencing and metabolic analyses in MAIT cell subsets in thymus and peripheral tissues from mice and humans to define the heterogeneity and developmental path of these innate-like lymphocytes. We show that the predominant mouse subset, which produces IL-17 (MAIT17), and the subset that produces IFN (MAIT1), have greatly different transcriptomes and metabolic states in the thymus and periphery. A subset has a transcriptome similar to circulating lymphocytes, and in mice these are found in recent thymic emigrants, suggesting partially mature cells emigrate from the thymus. Human MAIT cells are predominantly MAIT1 cells, but have a different metabolism from naïve CD8 T cells with increased fatty acid uptake and storage. Although mouse and human subsets are similar in thymus, in the periphery they are divergent, likely reflecting environmental and genetic differences. Single cell RNA sequencing of mouse MAIT cells from thymus, liver, lung and spleen.