Perhaps due to the large increase in the FOXP3+ Treg cell content and despite the key role of BLIMP1 in Il10 expression, NOD.Cd4-Cre Prdm1loxP/loxP mice developed neither type 1 diabetes (none of the 50 females and 21 males developed T1D for at least 28 wk of follow-up) nor colitis (no clinical signs of ulcerative colitis in any of the above mice and no pathological features of colitis in the three mice that were examined histopathologically; data not shown). The gene discussed is PRDM1; the disease is type 1 diabetes mellitus.