The tumor cell lines tested negative for mycoplasma infection and Plasmocin (InvivoGen) was used as a routine addition to the culture media to prevent mycoplasma contamination. The mice were inoculated with 1–1.5 × 105 B16F10-OVA cells or 2 × 106 MC38-OVA cells s.c. into the right flank. The mice were i.p. injected at the indicated time points with either 200 μg anti-PD-1 (29F1. A12, InVivoPlus anti-mouse PD-1, Bioxcell), anti-CTLA-4 (9H10, InVivoPlus anti-mouse CTLA-4, Bioxcell) or the respective isotype controls (anti-CTLA-4 isotype control, InVivoPlus polyclonal Syrian hamster IgG, Bioxcell; anti-PD-1 isotype control, InVivoPlus rat IgG2a isotype control, anti-trinitrophenol, Bioxcell). Tumor size was monitored every other day and tumors were harvested at the indicated time points for the analysis of tumor-infiltrating lymphocytes. Tumor volume was calculated as ½ × D × d2, where D is the major axis and d is the minor axis, as described previously45 (link). Tumor growth was monitored at least three times a week to ensure that the tumors did not exceed 25 mm in diameter.