CD4 and neoplasm: It has also been reported that naive tumor-specific CD4-positive T cells differentiate in vivo and eradicate established melanoma, tumor-responsive CD4-positive T cells improve cytotoxic activity and obliterate large established melanoma after transferring into lymphopenic hosts, and MHC-II-restricted cytotoxic T lymphocytes are generated by mature CD4-positive T helper cells [18–20].