immunology allergic disorders
Molecular Components of the Immune System
Acute Phase Reactants
Acute phase reactants are plasma proteins whose levels dramatically increase (called positive acute phase reactants) or, in some cases, decrease (called negative acute phase reactants) in response to the elevated circulating levels of interleukin (IL)-1 and IL-6 that occur when infection or tissue damage occurs. Most dramatically increased are: C-reactive protein (CRP) Serum amyloid A Other acute phase reactants include: Mannose-binding lectin Serum amyloid P component Alpha-1 acid glycoprotein Fibrinogen C-reactive protein,mannose-binding lectin, and serum amyloid P component activate complement and act as opsonins. Serum amyloid A and alpha-1 acid glycoprotein are transport proteins, and fibrinogen is a coagulation factor. Elevated C-reactive protein levels are a nonspecific indicator of infection or inflammation. Increased fibrinogen levels are the main reason the erythrocyte sedimentation rate (ESR) is elevated in acute inflammation. Many acute phase reactants are made in the liver. Collectively, they may help limit tissue injury, enhance host resistance to infection, and promote tissue repair and resolution of inflammation. 