Diversity and hallmarks of metabolites surveyed by MR1

Abstract

Mucosal-associated invariant T (MAIT) cells are one of the innate T cell subset. They are known to contribute to anti-bacterial response by recognizing bacterial components with invariant TCRs which are presented on a monomorphic antigen presenting molecule, MHC related protein 1(MR1). After years of uncertainty about the molecular entity of this bacterial antigen, they were recognized as vitamin B metabolites in 2012, and identified as 5-OP-RU in 2014. Recently, MR1 was found to contain a broad ligand-binding pocket, allowing recognition of compounds with various structures. In this review article, we will summarize the history of MR1 ligand discovery and discuss the potential new ligand structures that may uncover previously-unappreciated MAIT cell functions.