Editing Natural killer cell (section)

===Cytokine-induced NK and Cytotoxic T lymphocyte (CTL) activation===
[[Cytokine]]s play a crucial role in NK cell activation. As these are [[Stress (biology)|stress]] molecules released by cells upon viral infection, they serve to signal to the NK cell the presence of [[virus|viral pathogens]] in the affected area. Cytokines involved in NK activation include [[interleukin 12|IL-12]], [[interleukin 15|IL-15]], [[interleukin 18|IL-18]], [[interleukin 2|IL-2]], and [[CCL5]]. NK cells are activated in response to interferons or macrophage-derived cytokines. They serve to contain viral infections while the adaptive immune response generates antigen-specific [[cytotoxic T cells]] that can clear the infection. NK cells work to control viral infections by secreting [[IFNγ]] and [[TNFα]]. IFNγ activates macrophages for phagocytosis and lysis, and TNFα acts to promote direct NK tumor cell killing.  Patients deficient in NK cells prove to be highly susceptible to early phases of herpes virus infection. [Citation needed]