Fig.2. Depletion of CD4⁺CD25⁺ T regulatory cells leads to tumor rejection in mice regardless of vaccination.

3 and 1 day prior to vaccination, 1 mg anti-CD25 mAb (PC-61) or rat IgG mAb was injected ip. into BALB/c mice, and then 1×10⁵ irradiated (25,000 rad) CT26 cells as a vaccine were injected sc. into these mice. 3 weeks after vaccination, 1×10⁶ live CT26 cells were injected sc. into these mice. Tumors were measured by a caliper gauge, and tumor size was determined as the product of tumor length (mm) × tumor width (mm). Five female BALB/c mice were used for each group per each experiment. Mice were euthanized when the tumor area exceeded 1 cm², and the data were represented as percent survival. The results were pooled from two independent experiments. p<0.01 by log-rank test between control and vaccine alone group. p<0.0001 by log-rank test between control group and PC-61-treated groups with or without vaccination.