Second early wave of response. Regulatory pathways controlling production and action of IFN-γ during early HSV infection. When infected with HSV macrophages (Mφ) produce several cytokines, including IL-12, which stimulate production of IFN-γ, primarily in NK cells. IFN-γ then induces NO production in macrophages and stimulate the direct antiviral activity of IFN-α/β in other cells. Stimulatory pathways are indicated by green arrows (→), and inhibitory pathways are drawn in red.