Murine MAIT cells: phenotypic markers, plasticity, and parallels to humans

Mucosal-associated invariant T (MAIT) cells are innate-like T cells that recognize microbial metabolites. Recent studies have suggested numerous markers to define MAIT cells with distinct functional characteristics. This review synthesizes available data to identify markers that distinguish type 1 and type 3 murine MAIT cells. Inflammation can alter the expression of these markers, reflecting the plasticity of MAIT cells, which is discussed further. Comparative analysis with human MAIT cells reveals that type 1 and type 3 subsets are not as apparent. Although these have been described as activation states, unique human MAIT cell subsets exist across various tissues. By establishing a consensus for how to categorize MAIT cells, this review facilitates future research on these important lymphocytes.