These plasma proteins (in addition to fibrinogen) increase 25% or more in response to inflammation and injury are underdirect control of interleukin-6 (IL-6) (hepatocyte-stimulating factor). Other proteins which increase are ceruloplasmin, C3and C4 which increase 50% or more; alpha-1 acid glycoprotein, alpha-1 antitrypsin, haptoglobin and fibrinogen (the majordeterminant of viscosity 1 ) which increase two- to fourfold; C-reactive protein (CRP) and serum amyloid A which increaseseveral hundred-fold. Despite long-held clinical opinion to the contrary, available data indicate that neither ESR normeasurement of specific acute-phase reactants are useful in excluding underlying infection or inflammation regardless ofthe pretest probability. These proteins are secreted into the blood in increased or decreased quantities by hepatocytes inresponse to trauma, inflammation, or disease. They can serve as inhibitors or mediators of the inflammatory processes.Certain acute-phase proteins have been used to diagnose and follow the course of diseases or as tumour markers.