CD25 depletion before tumor challenge promotes partial tumor infiltration in the absence of Gvax/αCTLA-4. Mice were challenged with B16/BL6 melanoma tumor cells and treated or not treated with anti-CD25 mAb 4 d before or after tumor challenge. 14 d after tumor implantation, tumors were harvested and analyzed for the expression of CD8 and Foxp3 by flow cytometry (A) or CD8 (green) and CD31 (red) by confocal microscopy (B). Bar, 100 μm.