CTLA4 and neoplasm: Anti-CTLA-4 antibodies can reactivate and relieve the immunosuppression of CD4+ and CD8+ T cells, enhance the activation and proliferation of effector T cells, and reduce the immunosuppressive effect of regulatory T cells (Tregs) through antibody-dependent cellular cytotoxicity (ADCC), further reducing the presence of Tregs in tumor tissues (3).