IFNG and cancer: An 11‐year prospective study of 3500 middle‐aged and elderly people showed an increased incidence of cancer in patients with low initial NK cytotoxicity.67 It has been observed that the level of IFN‐γ produced by NK cells in the elderly and stimulated by IL‐2 or IL‐12 decreased (Table 2),44 and migration of NK cells decreased with age (Table 2).5 After a virus attacks the body, NK cells collect in a number of draining lymph nodes.