The release of physiologically active proteins by the liver into the blood in response to interleukin-6 or other cytokines that participate in the destruction of pathogens and promote healing during inflammation. This results in fever, an increase in circulating neutrophils, and activation of the hypothalamus, pituitary gland , and adrenal gland s. The acute phase response involves the production of plasma proteins as well as other metabolic, hematological, and neuroendocrine events. Cytokines, produced by white blood cells, esp. macrophages, stimulate the liver's production of acute phase proteins: interleukin-6, interleukin-1β, tumor necrosis factor α, interferon-Γ, and transforming growth factor β. These proteins, which increase or decrease in the blood by at least 25%, include C-reactive protein, complement, and coagulation factors; they enhance the immune response and tissue repair. Cytokines also stimulate systemic changes, producing diverse beneficial effects including fever, which enhances the immune response and stabilizes cell membranes; increased adrenal cortisol and catecholamine production, which helps maintain hemodynamic stability; thrombocytosis and leukocytosis; and increased gluconeogenesis and lipolysis, which provide nutrients for cells. There are also negative effects, however, including decreased production of erythropoietin, causing anemia; impaired growth; anorexia; lethargy; and , if prolonged, the loss of skeletal muscle and fat (cachexia).

SYN: acute phase response..

SEE: cytokine; inflammation; interleukin-6; protein, acute phase.