CTLA4 and anti–IL-2 can substitute for Tregs in restoring effector T-cell bias. DT-treated Foxp3^DTR mice were treated with CTLA4-Ig on day 5 or anti–IL-2 Ab on days 0-8. (A) Frequency of IL-4 and IFNγ producers among CD4⁺CD44^hiFoxp3⁻ T cells and (B) Th2/Th1 ratio in wild-type mice, DT-treated Foxp3^DTR mice, DT-, and CTLA4-Ig–treated Foxp3^DTR mice and DT- and anti–IL-2-treated Foxp3^DTR mice, after 9 days of treatment with DT. All data are from the spleen (n = 3-4/group). (C) The effect of CTLA4-Ig or anti–IL-2 Ab on apoptosis in Th1 and Th2 subsets in the absence of Tregs, measured by calculating the percentage change in activated caspase 3 expression in DT-treated mice (diamonds), DT-treated CTLA4-Ig–treated mice (squares) or DT-treated anti–IL-2-treated mice (circles), compared with wild-type mice (dashed line at 100%). Each symbol represents an individual mouse, P values represent significant differences in CTLA4-Ig– or anti–IL-2 Ab-treated mice versus Treg depletion alone. Error bars indicate SD.