Properties of acute phase proteins of human plasma

Almost 50 years ago the term acute phase serum was used for the first time by Avery and his colleagues to characterize serum from patients in an acute state with inflammatory diseases and which contained C-reactive protein. In the meantime a variety of proteins was detected in human blood plasma which are subject to the acute phase response. About a fifth of the until today more than hundred isolated and well characterized plasma proteins are to be classified as acute phase proteins. In human plasma they exist in many various quantities. There is no functional relationship among acute phase proteins. They partly belong to the coagulation system or to the complement system or they are transport proteins and inhibitors. There's also no relationship regarding their physico-chemical properties. The majority of the acute phase proteins are glycoproteins of different molecular weight. However, CRP and SAA, which serum concentration can rise to one thousandfold above normal during an acute inflammatory process, are pure polypeptides. The interpretation of the present knowledge about the functional activities of the acute phase proteins has led to the opinion that they probably all play a role during inflammatory processes. It is believed that the acute phase response represents a physiological mechanism which provides the site of inflammation via the tissue fluid with increased concentrations of these proteins. The majority of the acute phase proteins is synthesized in hepatocytes. The stimulation of the synthesis is probably mediated through cytokines (IL1) which are released from macrophages at the site of tissue damage.