To assess whether the proportional increase in effector Treg cells correlated with an enhanced suppressive function in vivo, we employed a naïve CD4+ T cell adoptive transfer colitis model, in which CD4+ T cell-mediated disease in recipient Rag2-deficient mice is accompanied by several pathological changes including body weight reduction, infiltration of immune cells and loss of colonic crypt structure (Kiesler et al., 2015). The gene discussed is CD4; the disease is colitis.