Major histocompatibility complex class I-related protein 1 (MR1)

Major histocompatibility complex class I-related protein 1 (MR1) is a non-classical, monomorphic antigen-presenting molecule that presents small metabolite antigens, especially intermediates from microbial riboflavin biosynthesis, to a population of T cells called mucosal-associated invariant T (MAIT) cells. MR1 consists of α1, α2, and α3 domains, and acquires ligand in the endoplasmic reticulum before associating with β2-microglobulin for cell-surface expression. MR1 is mostly intracellular and requires antigen binding for stable surface expression; its primary immune function is to mediate rapid activation of MAIT cells, which can then kill infected cells and secrete cytokines in context of infection or cancer. MR1 plays a critical role in the immune surveillance of infection and tumors, particularly by enabling immune detection of cells harboring microbes capable of vitamin B biosynthesis. Research into direct pharmacological targeting is ongoing, largely focused on modulating MAIT cell responses in cancer and infectious disease.

Other names

MHC class I-related gene proteinMHC-class I-related protein 1MR1HMR1

Antigen presentation of small molecule metabolites (mainly derived from microbial vitamin B2 (riboflavin) synthesis) to MAIT cells, leading to MAIT cell activation and immune effector functions