RAG1 and colitis: In the absence of IL2 expression in Rag1–/– × Rorc-Cre × Il2fl/fl mice, more severe colitis is induced upon adoptive transfer of naïve CD4+ T cells, compared with Rag1–/– × Il2fl/fl mice, demonstrating the relevance of ILC3-derived IL2 in modulating pathogenic T cells [5].