Mucosal associated invariant T cells: don't forget your vitamins

Abstract

T lymphocytes express clonal receptors, called T cell receptors (TCRs), which specifically recognize antigens presented in combination with major histocompatibility molecules (MHC). To date, T cell antigens can be broadly categorized into two classes: peptides and lipids. A recent paper published in Nature by Kjer-Nielsen and colleagues reveals that a unique population of T lymphocytes expresses TCRs that recognize a completely new and unexpected class of antigens, vitamin metabolites.

Figure 1

Three broad classes of ligands recognized by TCRs: peptides, lipids, and vitamin metabolites. Examples of each class of ligands are shown. Peptides from MCMV and flagellin are presented by MHC class I or class II to classical αβ T cells, respectively. Vitamin metabolites are presented to MAIT cells by MR1. The lipids, α-galactosylceramide (αGalCer) and dideoxymycobactins presented to NKT cells and CD1a-restricted T cells, respectively.