MAIT cells in immune-mediated tissue injury and repair

Mucosal-associated invariant T (MAIT) cells are T cells that express a semi-invariant alpha beta T-cell receptor (TCR), recognizing non-peptide antigens, such as microbial-derived vitamin B2 metabolites, presented by the nonpolymorphic MHC class I related-1 molecule. Like NKT cells and gamma delta T cells, MAIT cells belong to the group of innate-like T cells that combine properties of the innate and adaptive immune systems. They account for up to 10% of the blood T-cell population in humans and are particularly abundant at mucosal sites. Beyond the emerging role of MAIT cells in antibacterial and antiviral defenses, increasing evidence suggests additional functions in noninfectious settings, including immune-mediated inflammatory diseases and tissue repair. Here, we discuss recent advances in the understanding of MAIT cell functions in sterile tissue inflammation, with a particular focus on autoimmunity, chronic inflammatory diseases, and tissue repair. MAIT cells have dual functions in immune-mediated tissue injury and repair. Depending on the context, MAIT cells can exacerbate inflammation and tissue injury by producing pro-inflammatory cytokines and cytotoxic molecules or mediate tissue protection by regulating other immune cell subsets and secreting tissue repair factors.image