The major function of NK cells in viral infections and cancer is lysis of target cells by rapidly releasing cytolytic mediators such as perforin and granzyme B and/or secretion of inflammatory cytokines which include but are not limited to interferon (IFN)-γ, tumor growth factor (TGF), tumor necrosis factor (TNF), interleukin (IL)-6, IL-10, granulocyte macrophage-colony stimulation factor (GM-CSF), and G-CSF. The gene discussed is TNF; the disease is viral infectious disease.