CD4 and Chronic colitis: Using a model of T-cell-induced colitis, a murine model of human inflammatory bowel disease (IBD) induced by naïve CD4 T cells transferred into immunodeficient recipients, we demonstrated that while transfer of naïve wild type CD4 T cells into Rag−/− recipients induces chronic colitis that develops ~4 weeks after transfer, the same CD4 T cells transferred into IFNγR−/− Rag−/− recipients induce acute fulminant colitis within 7 days after transfer [26].