Overview of Acute-Phase Proteins
المؤلف:
Mary Louise Turgeon
المصدر:
Immunology & Serology in Laboratory Medicine
الجزء والصفحة:
5th E, P93-94
2025-07-07
639
The acute-phase response is an innate body defense. This response is a nonspecific indicator of an inflammatory process.
Overview A group of glycoproteins associated with the acute-phase response are collectively called acute-phase proteins or acute-phase reactants. The various acute-phase proteins rise at different rates and in varying levels in response to tissue injury (e.g., inflammation, infection, malignant neoplasia, various diseases or disorders, trauma, surgical procedures, drug response). The increased synthesis of these proteins takes place shortly after a trauma and is initiated and sustained by proinflammatory cytokines.
The main biological sign of inflammation is an increase in the ESR. In addition to the ESR, measurement of the plasma concentration of acute-phase reactants is usually a good indicator of local inflammatory activity and tissue damage. More than 20 acute-phase proteins have a definable role in inflammation (Box 1). These reactants constitute most of the serum glycoproteins (Table 1).
Box1. Major Applications of Acute-Phase Protein Measurements
Table1. Examples of Clinically Useful Acute-Phase Proteins
Acute-phase reactants include C-reactive protein (CRP), inflammatory mediators (e.g., complement components C3 and C4), fibrinogen, transport proteins such as haptoglobin, inhibitors (e.g., α1-antitrypsin), and α1-acid glycoprotein. Profiles of inflammatory changes yield detailed information but rarely provide major evidence for diagnosis or treatment.
Produced by the liver under the control of IL-6, CRP is a parameter of inflammatory activity. Serum concentrations can increase 1000-fold with an acute inflammatory reaction. Persistent increases in CRP can also occur in chronic inflammatory disorders (e.g., autoimmune disease, malignancy).
CRP is prominent among the acute-phase proteins because its changes show great sensitivity. Changes in CRP are independent of those of ESR and parallel the inflammatory process. CRP is a direct and quantitative measure of the acute-phase reaction and, as a result of its fast kinetics, provides adequate information about the actual clinical situation. In contrast, ESR is an indirect measure of the acute-phase reaction. It reacts much slower to changes of inflammatory activity and is influenced by other factors. ESR can be falsely normal in conditions such as polyglobulinemia, cryoglobulinemia, and hemoglobinopathy. ESR may also be spuriously high in the absence of inflammation in patients with anemia or hypergammaglobulinemia.
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