To assess the role of IL-23R expression on T cells in the development of colitis, we transferred CD4+CD45RBhi cells isolated from wild-type (WT) or Il23r−/− mice into B and T cell-deficient Rag1−/− mice, with the latter allowing us to restrict IL-23 responsiveness to the innate immune compartment. The gene discussed is RAG1; the disease is colitis.