MAIT cells phenotype in metabolic diseases. Blood MAIT cells frequency is reduced in metabolic diseases, which could reflect their recruitment to inflamed and dysfunctional tissues. MAIT cells express a chronically overactivated phenotype and at the same time, are refractory to TCR activation. They display an increase in proliferation as well as signs of cellular exhaustion (CD25, CD69, PD-1) and abnormal apoptosis (reduction of BCL-2). Moreover, they produce abnormal levels of Th1, Th17 and cytotoxic factors. Taken together, this indicates major MAIT cell alterations, including loss of antibacterial function.