Lymphoreplete hosts tyreated with Treg depletion show superior survivals compared with hosts receiving preimmunotherapy irradiation or activated T cells. Tumor growth curves (left) and survival curves (right) of treated groups as shown. Radiation therapy (500 cGy) administered to groups shown on day −1, B16 tumors inoculated subcutaneously on day 0, and pmel-1 cells administered on day 3. Where indicated, pmel-1 cells were activated before transfer as described in “Methods.” Results representative of 2 separate experiments (n = 4 or 5/group in each experiment). *P < .05.