Acute Phase Proteins

Inflammation is a complex defense mechanism essential against several biological, chemical, or physical injuries to organisms. The acute phase response is crucial to the systems’ competence to successfully overcome to this injury. The response consists of modifications in the concentration and structure of some plasma proteins known as “acute phase proteins.” The elevations in the concentrations of these proteins can aid host defense by helping to identify pathogen microorganisms, mobilization of leukocytes from circulation to injured or infected sites. Various classifications are proposed for acute phase proteins (APPs) like positive or negative and major, moderate and minor proteins. Although there are many proteins, only a few have taken their place in clinical use. Especially erythrocyte sedimentation rate, C-reactive protein, procalcitonin, and serum amyloid-A are proteins that are frequently studied. Hepatocytes stimulated by pro-inflammatory cytokines are responsible for the synthesis of most of the positive APPs in the glycoprotein structure. Various immunological and immunoradiometric-based test methods are available to detect both APPs and associated cytokines. APPs are not specific inflammation markers, and the tests used should be interpreted carefully. The classifications and regulation of APPs by cytokines, and the APPs commonly used in clinical practice are reviewed in this article.