We induced experimental colitis by transfer of CD4+CD25− isolated T cells into RAG2−/− (T and B cell deficient) mice and treated these mice with tofacitinib for 5–6 weeks either with a dosage of 10 or 40 mg/kg body weight immediately after CD4+ transfer or started treatment after first symptoms of disease for several weeks. This evidence concerns the gene RAG2 and colitis.