CD4 and neoplasm: The combined anti-PD-1/CD137 treatment also increased the absolute number of splenic CD4+ T cells and percentage of peritoneal effector CD4+ T cells; however, it appeared that CD4+ T cells are dispensable for tumor protection in this model since removal of CD4+ T cells had little effect on antitumor effect triggered by combined anti-PD-1/CD137 and cisplatin treatment.