Mucosa-associated invariant T cells (MAIT cells) recognize riboflavin metabolites displayed via the antigen-presenting molecule MR1. In the Proceedings of the National Academy of Sciences, Sandberg and colleagues investigate potential heterogeneity in the response of human MAIT cells to either Escherichia coli or Candida albicans. Although both of these microbes possess riboflavin biosynthesis pathways, they elicit distinct responses from MAIT cells, with the response to E. coli being generally more robust and polyfunctional with greater T cell receptor (TCR) downregulation. The TCR Vβ usage also influences the strength and tone of the MAIT cell response, which is suggestive of the recognition of distinct ligands. Analysis of the MAIT cell surface proteome and transcription factors reinforced their distinction from other T cell subsets. The findings also highlight a degree of functional heterogeneity, with MAIT cells that express the markers CD56, CD84 and CD94 having more potent responses to stimulation by IL-12 plus IL-18.

Proc. Natl. Acad. Sci. USA (19 June 2017) http://dx.doi.org/10.1073/pnas.1705759114