RAG1 and colitis: We found that isolated oral Th17 cells (ie, Kaede red cells isolated from the gut of ligatured mice) induced colitis when transferred intravenously into Rag1−/− mice colonized by the oral pathobiont K aerogenes in the gut associated with an increase of Th17 cells (RORγt+) and Th1/Th17 cells (RORγt+ T‐bet+); in contrast, Kaede green cells isolated from the gut of ligatured mice failed to cause colitis.