DT-mediated Treg depletion improves anti-tumor immunity in young but not aged tumor-bearing mice. (A–C) Young and aged C57BL/6 mice challenged with OVA expressing B16 melanoma and treated as in Fig. 1. A, Spleen OVA-specific CD8+ T cells prevalence. B, Spleen IFN-γ+ CD4+ and CD8+ T cells prevalence. (NT = no tumor, naïve controls). (D, E) Young and aged Foxp3DTR mice challenged with B16 and treated with 15 µg diphtheria toxin (Dipht. Tox)/kg or PBS. D, Tumor growth in young and aged Foxp3DTR mice. E, Prevalence of IFN-γ+ CD4+ and CD8+ T cells and OVA-specific CD8+ T cells. Values are mean ± SEM.