In murine models of infection, interferon gamma (IFN-γ) has been shown to act in synergy with another macrophage derived cytokine, tumor necrosis factor alpha (TNF-α), in activating macrophages to synthesize nitric oxide (NO), a potent microbicidal agent that leads to killing of intracellular parasites [7], [8]. The gene discussed is TNF; the disease is infection.