MR1 and systemic lupus erythematosus: To investigate whether MAIT cells contribute to the pathological process of lupus, we crossed MAIT cell-deficient MR1 knockout mice with FcγRIIb−/−Yaa mice and compared the disease course of MR1−/−FcγRIIb−/−Yaa mice and littermate MR1+/+FcγRIIb−/−Yaa mice (henceforth referred to as MR1−Fc− and MR1+Fc− mice, respectively).