TNF and colitis: Although the recipient Rag1−/− mice reconstituted with CD4+ CD45Rbhi T cells and Blimp1‐deficient Tregs developed less severe colitis compared with that reconstituted with CD4+ CD45Rbhi T cells alone, they displayed more severe colitis compared to the mice receiving CD4+ CD45Rbhi T cells and WT Tregs, as evidenced by increased weight loss, higher pathological scores, and elevated levels of intestinal TNFα and IL‐6 (Figure 4D–H).