CD4 and neoplasm: Although the cellular mechanism of OX40 antibody underlying anti-tumor immunity is not completely clear, its action has been widely recognized to contain three potential modes: (1) directly stimulating CD4+ and CD8+ T cells by enhancing their proliferation and survival; (2) inhibiting Tregs by reducing their suppressive function; (3) directly deleting intratumoral Tregs by engaging Fcγ receptors on effector cells (13, 14).