Mice were inoculated with ID8 cells and on day 25 received either 200 μg hamster IgG (Jackson ImmunoResearch Laboratories, West Grove, PA) or 200 μg G4 clone PD-1–blocking monoclonal antibody i.p. as described (21 (link), 22 (link)). Mice were treated until moribund up to 11 treatments (8 - 11 times up to 7 weeks). IL-10 neutralizing antibody (BioLegend, San Diego, CA) and IL-10R antagonist antibody (BD Pharmingen, San Diego, CA) were injected i.p alternating between the two antibodies at a concentration of 100 μg and 200 μg per mouse, respectively. The same amount of isotype matched antibodies (Rat IgG1κ or Rat IgG1χ) from the respective suppliers was injected in the control groups. Tumor and ascites were harvested as necessary when mice were moribund.