CD4 and neoplasm: By targeting receptors such as PD-1(in CD8+ T cell or CD4+ T cell) and CTLA-4 (in Naive CD4+ T cell) or their ligands (e.g., PD-L1), ICIs mitigate immunosuppressive signaling within the tumor microenvironment, thereby reactivating T cell activation and proliferation, enabling renewed recognition and elimination of tumor cells, and ultimately exerting antitumor effects [118–120].