Treatment of combined anti-PD-1/GITR mAb induced tumor-specific long-lasting immunity against ID8 ovarian cancer. A, The typical presentation of ID8 ovarian cancer in C57BL/6 mice. The left and right picture shows the macroscopic appearance of ascites and ID8 tumor mass in peritoneal cavity of mice respectively. B, Mice (10 mice/group) were transplanted i.p. with 5 × 106 ID8 cells on day 1 and treated with 250 μg of control, anti-PD-1, anti-GITR and anti-PD-1/GITR mAb on day 8, 11 and 15. Mean survival time of tumor-bearing mice was calculated. C, Overall survival of mice was recorded. D, The peritoneal tumor masses were weighed when mice were euthanized with each dot representing each mouse. E, Long-term surviving (90 days after first tumor challenge) mice from combined mAb treatment group were rechallenged with ID8 cells and their overall survival was recorded. Naïve mice were challenged with ID8 cells as control. F, Mice (5 mice/group) treated with combined anti-PD-1/GITR mAb were also injected with an anti-CD4, anti-CD8, anti-NK1.1, or control mAb with 500 μg of each mAb per mouse 1 day before and two days after tumor challenge followed by injection of 200 μg every 5 days thereafter for the duration of the experiments and their overall survival were recorded. Data are representative of 2 independent experiments for B-E. **P < 0.05, ***P < 0.001, combined mAb vs control or single mAb.