However, we and other groups have reported that depletion of CD4+ cells using a depleting monoclonal antibody results in strong antitumor effects in murine tumor models (4–6) and induces robust antitumor effects when administered synergistically with immune checkpoint inhibitors including anti-PD-1/PD-L1 antibody and anti-CTLA-4 antibody (7). Here, PDCD1 is linked to neoplasm.