CD4 and neoplasm: In poorly immunogenic tumor models, such as B16 melanoma, spontaneous CD8+ T cell-mediated anti-tumor immunity rarely develops; however, deletion of CD4+ T cells in B16 tumor-bearing mice uncovers a robust endogenous tumor antigen specific CD8+ T cell response capable of inducing tumor regression, manifest as an abscopal effect; furthermore, adoptive transfer of CD8+ and CD4+ T cells in Rag1−/− mice, lacking CD4+CD25+ compartment elicited the robust concomitant immunity that was attenuated with the addition of CD4+CD25+ cells [23].