MAIT cells: programmed in the thymus to mediate immunity within tissues

MAIT cells are an evolutionarily conserved T cell subset recognizing ubiquitous microbial metabolites. Herein, we review recent literature showing that MAIT cells can be divided into type 1 and type 17 subsets, which acquire a tissue resident differentiation program in the thymus and localize in specific tissues. We also discuss the nature and in vivo availability of the different agonist and antagonist MAIT ligands with potential consequences for MAIT cell biology.