MAF and colitis: To test whether the defect of MAF in Treg was sufficient to recapitulate the phenotype of colitis, we generated Foxp3YFPcreMaffl/fl mice (MafΔTreg), in which only Treg are inactivated for the expression of Maf. We observed a strong decrease in percentages as well as total numbers of RORγt+ Treg in the colon and in the mLN, mirrored by a slight increase in percentages of RORγt− Treg and TH17 cells (Fig. 5A,C and Supplementary Fig. 3).