Inhibition of high-affinity IL-2Rα during lymphopenia depletes T_Regs. (A-C) Untreated or TMZ-lymphodepleted C57BL/6 mice received OVA vaccination with or without concomitant αIL-2Rα mAb treatment (n = 5/group). One week after mAb administration and vaccination, mice were bled and CD4⁺CD25⁺Foxp3⁺ T_Reg levels in the peripheral blood were assessed by FACS analysis. Experiments performed in at least triplicate with similar results. (A-B) For frequency T_Regs: *P = .0154, **P = .0027, and ***P = .0001. By 2-way ANOVA with interaction, the magnitude of effect of anti–IL-2Rα mAb was greater among TMZ-treated mice as opposed to mice not treated with TMZ (P = .0024). For absolute number of T_Regs, *P = .0025. (C) In the untreated and TMZ-treated cohorts, the percentage depletion of CD4⁺CD25⁺Foxp3⁺ T_Regs after αIL-2Rα mAb administration was determined from the absolute number of T_Regs after αIL-2Rα mAb treatment in comparison with the absolute number of T_Regs in the cohort that did not receive IL-2Rα blockade.