Given reports suggesting that the increases in Treg (CD4+CD25+Foxp3+) induced by helminth infections are critically involved in the anticolitic effects of these parasites [23–26], we used a Foxp3 reporter mouse to evaluate the percentages of T regulatory cells in the spleen and peritoneal cavity during T. crassiceps infection and DSS-induced colitis. The gene discussed is FOXP3; the disease is colitis.