In the absence of Tregs, adoptive transfer of naive CD4+ T cells (CD45RBhiCD25−CD4+) into Rag1−/− mice induced severe colitis, as indicated by weight loss (Fig. 4C), shortened colon (Fig. 4, D and E), damaged intestinal tissues (Fig. 4F), and greatly increased proinflammatory IFNγ+CD4+ T cells in the colon (Fig. 4G) and mLN (fig. Here, CD4 is linked to colitis.