Vaccination of plasmids expressing IL-21 and IL-15 promoted the expansion of CD8+ memory T-cells and enhanced CD8+ T-cell responses against viral antigens, which was partially independent on CD4+ T-cell help [80], whilst coexpression of IL-21 and IL-7 in a whole-cell cancer vaccine enhanced anti-tumour immunity dependent upon both CD4+ and CD8+ T-cells capable of generating effector memory cells associated with tumour infiltration and long-term anti-tumour function in murine models [81]. The gene discussed is CD4; the disease is cancer.