Flu-Like Syndrome and Cytokines

Flu-like reactions have been described, long before the introduction of therapeutic cytokines, in the clinical setting to treat a variety of pathological conditions. Indeed, flu-like reactions are commonly associated with vaccination as well as a number of infectious diseases unrelated to the influenza virus. Flu-like symptoms have also been described after the early use of supposedly immunostimulating drugs. When the first interferon formulations began to be used to treat cancerous patients, flu-like symptoms with some variation according to the type of interferon, route of administration, schedule, and dose, were observed in most patients. Since then, the flu-like syndrome emerged as a common-if-not universal complication of therapeutic cytokines.