MR1 and obesity due to melanocortin 4 receptor deficiency: We first analyzed MAIT cell alteration occurring in obese C57BL/6J (B6) mice, which were either fed high-fat diet (HFD) or deficient for leptin (ob/ob mice), then we deciphered the impact of MAIT cells in obesity using Vα19 transgenic B6 mice expressing elevated frequency of MAIT cells and MR1−/− B6 mice devoid of MAIT cells.