CD8A and neoplasm: Lymphocyte subset depletion experiments demonstrated that tumor protection by anti-PD-1/OX40 mAbs was dependent on the CD4+ and CD8+ T cells as removal of CD4+ or CD8+ T cells but not NK cells completely abrogated the antitumor effect conferred by anti-PD-1/OX40 mAb treatment (Figure 1E).