Although Treg cell-specific deletion of Ddb1 led to impaired stability and function of Treg cells and development of early onset fatal autoimmune disease (manuscript in preparation), our data with experiments with both mixed bone marrow chimera and mixed SMARTA transfer suggested that Ddb1 was required for TFH and Th1 cell generation by controlling CD4+ T-cell expansion in a cell-intrinsic manner. Here, DDB1 is linked to autoimmune disease.