CD4 and neoplasm: Mechanistically, IT delivery of IL-12 plasmid applied once in B16F10 cells resulted in 70% (14 of 20) of tumor remission in treated animals, with significant therapeutic effects against untreated tumors; the lack of perforin or IFN-γ and the blockage of CD8+ T cells abolished IL-12 GET efficacy, whereas the blockage of CD4+ T cells or NK cells did not.