PDCD1 and neoplasm: The anti-tumor effects of anti-PD-1 antibody treatment were examined in the following four groups: mice injected with CB followed by normal rat IgG (control group), mice injected with CB followed by anti-PD-1 antibody (PD-1 group), mice injected with STZ followed by normal rat IgG (STZ group), and mice injected with STZ followed by anti-PD-1 antibody (STZ + PD-1 group) (Fig. 1A).