Treg depletion inhibited melanoma growth. B16F10 cells were injected s.c. on day 0 into the flank of mice. No PD1 antibody was administered. (A and B) Tumor growth curve (A) and frequencies of B cells, CD4 T cells, and CD8 T cells in the peripheral blood (B) on day 20 (n = 3–5 per group). (C) Tumor growth curve in the presence of cell depleting antibodies. Anti-CD4, anti-CD8, anti-NK1.1, or control IgG were injected i.p. into WT mice on days 0, 3, 6, 9, 12, and 15 after tumor inoculation to deplete the corresponding cells (n = 5 per group). (D) Tumor growth curve in Foxp3-DTR mice. 1 μg diphtheria toxin (DT) per mouse was injected i.p. on a daily basis for five consecutive days (day −5 to −1) to deplete Treg (Foxp3+ cells) in Foxp3-DTR mice (Foxp3-DTR with DT) (n = 4–8 per group). Data points represent individual mice in B. Data are representative of two independent experiments (A–D). WT C57BL/6J mice from JAX were used as controls (A–D). Error bars indicate SD (B) or SEM (A, C, and D). P values were determined by two-way ANOVA with post-hoc Tukey test (A–D). *P < 0.05; ***P < 0.001.