In vivo depletion of CD4⁺CD25⁺ T_Reg cells enhances the efficacy of posttransplantation DC vaccination in treating preestablished lymphoma. Syngeneic transplantation was set up as described in Figure 1A except that no transgenic HA-specific T cells were used. Seven days after transplantation, mice were treated with either 0.3 mg PC61 or the control rat Ig daily for 3 days. Fourteen days after transplantation, mice were vaccinated with mature DCs pulsed with either HA peptide (DC-HA) or a control peptide (DC-Con) and monitored for tumor-free survival. Data (n = 10) represent percentages of tumor-free survival over time from the transplantation (day 0).