RAG2 and colitis: To find out if the reduced Treg cells in the “T + KOTreg” group was due to fate conversion, we transferred Thy1.1+CD45RBhigh pathogenic T cells and Thy1.2+Ctrl Treg or Thy1.2+KO Treg cells to Rag2–/– mice, which were sacrificed for analysis when the mice developed colitis (Supplementary Fig. 3b).