The inhibition of Tregs augments antitumor responses in reconstituted mice. (A) Lymphodepleted mice were transferred intravenously with 40 × 10⁶ naive spleen cells and then injected SD with MCA205 tumor cells. Next, these mice were treated with anti–CD25 mAb (PC61) to inhibit CD4⁺CD25⁺Foxp3⁺ Tregs. Twelve days later, the percentage of CD4⁺CD25⁺Foxp3⁺ Tregs in the TDLN cells were assessed by FACS analysis. Treatment with PC61 significantly reduced the percentage of CD4⁺CD25⁺Foxp3⁺ Tregs. (B) Reconstituted mice were inoculated subcutaneously with 1 × 10⁵ MCA205 tumor cells. On the same day, mice were injected intraperitoneally with PC61. The combination of lymphodepletion, spleen cell transfer, and PC61 treatment significantly suppressed skin tumor growth.