The enhanced regulatory function of Ctsw−/− pTreg cells was further evaluated in a T cell cotransfer colitis model.WT CD4+CD25−CD45RBhi cells were transferred into Rag2−/− mice, together with either WT or Ctsw−/− in vitro–differentiated Foxp3+ (GFP) pTreg cells at a ratio of 10:1. The gene discussed is RAG2; the disease is colitis.