RAG1 and colitis: During colitis induced by adoptive transfer of CD45RBhi cells into Rag1-/- mice, RORγt-deficient Treg cells lost their suppressor function and acquired Th1-like effector phenotype, leading to severer colitis, suggesting that RORγt promoted Treg cells function as well as prevented Th1-like effector program in Treg cells (66).