Mucosal associated invariant T (MAIT) cells represent an abundant, innate-like T cell population, recognizing riboflavin metabolites of bacterial or yeast origin. They play a role in the defence against bacterial infections, but are also altered in viral infections and other inflammatory conditions. We have analysed MAIT cell frequencies, functional phenotype and cytokine production in patients with multiple sclerosis (MS), the most frequent inflammatory disease of the central nervous system. Evidence for an involvement of MAIT cells in MS immunopathology includes their presence in brain lesions and increased IL-17 production in MS patients