Mice developed colitis 6 weeks post transfer when naïve T cells were administered alone, while Treg co-transfer prevented colitis (figure 4A–C) in agreement with previous reports.26 Fc-effector, but not Fc-null, anti-CTLA4 treatment impairs Treg-mediated suppression of colitis (figure 4A–C). This evidence concerns the gene CTLA4 and colitis.