Increase or decrease in the concentration of certain proteins, or other substances, including micronutrients, in blood serum, following infections or tissue- inflammatory reactions. This reaction represents the body’s normal response in counteracting the deleterious effects of a noxious stimulus, but the changes in distributions of proteins and nutrients between body compartments can confound attempts to measure nutrient status by blood assays in those situations where an acute phase reaction is present. Its presence can be monitored, e.g. by measuring C-reactive protein (CRP) or arantichymotrypsin (ACT), both of which are increased by infections or inflammation, in serum or plasma.
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. 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 a, interferon- -y, 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).