CD4 and melanoma: Transfer of in vitro pre-activated NK cells with IL-18, IL-12 (another inducer of IFN-γ) and IL-15 (activator of NK cells) in a melanoma mouse model under radiation therapy enhanced antitumor immunity and decreased lung metastases, by increasing the accumulation and cytotoxicity of in vivo NK cells that required the presence of CD4+ T cells [116].