PDCD1 and neoplasm: To test the effect of tumor sialylation on the ability of ICB to reinvigorate tumor-infiltrating CD8 T cells, we subcutaneously injected mice with wild-type or GNE-KO MC38 tumor cells and treated mice bearing palpable tumors with four doses of PD-1–blocking antibodies alone or in combination with CTLA-4–blocking antibodies (Fig. 1H).