MHC class I-related protein (MR1) (MR1)

MHC class I-related protein (MR1) is a non-polymorphic, antigen-presenting molecule that is highly conserved across mammalian species [UniProt Q95460]. Unlike classical MHC class I molecules that present peptide antigens, MR1 is specialized to present small-molecule metabolites, particularly those derived from the riboflavin (vitamin B2) biosynthetic pathway found in many bacteria and fungi [PubMed: 24695216]. These metabolites are presented to mucosal-associated invariant T (MAIT) cells, a unique population of innate-like T cells that play a vital role in the early immune response to infection [PubMed: 22437502]. Upon recognition of the MR1-ligand complex, MAIT cells rapidly produce pro-inflammatory cytokines such as IFN-gamma and TNF, and exert cytotoxic activity against infected cells [PubMed: 25848865]. MR1 is also implicated in the detection of certain cancer cells, suggesting a role in tumor immunosurveillance that is independent of traditional peptide-based recognition [PubMed: 31959982]. Consequently, MR1 is an emerging therapeutic target for infectious diseases, autoimmune conditions, and oncology, with small-molecule ligands being developed to modulate MAIT cell activity [PubMed: 31959982]. This target represents a novel axis in immunotherapy, bridging innate and adaptive immunity through the presentation of non-peptide antigens.

Other names

Major histocompatibility complex class I-related gene proteinMR1

Presentation of microbial or synthetic small-molecule metabolites to the T-cell receptor of mucosal-associated invariant T (MAIT) cells, leading to their activation and effector function.