Selective depletion of T_regs enhances anti-CD137 therapy. BALB/c mice were inoculated subcutaneously with 5 × 10⁶ A20 tumor cells. Mice then received 1 intraperitoneal injection of either rat IgG or anti-CD137 mAb at day 6 after tumor inoculation. FR4 depletion was initiated before tumor challenge as described in “Depletion of NK cells, CD4 T cells, CD8 T cells, and Tregs.” Groups include the following: rat IgG alone, rat IgG + anti-FR4, anti-CD137 mAb alone, and anti-CD137 mAb + anti-FR4. Mice were then monitored for tumor growth (A) and overall survival (B).