Acute phase protein
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Acute-phase proteins are a class of proteins whose plasma concentrations increase (positive acute phase proteins) or decrease (negative acute phase proteins) in response to inflammation. This response is called the acute-phase reaction (also called acute phase response).
In response to injury, local inflammatory cells (neutrophil granulocytes and macrophages) secrete a number of cytokines into the bloodstream, most notable of which are the interleukins IL-1, IL-6 and IL-8, and TNF-α.
The liver responds by producing a large number of acute-phase reactants. At the same time, the production of a number of other proteins is reduced; these are therefore referred to as "negative" acute phase reactants.
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[edit] Positive
Positive acute-phase proteins serve different physiological functions for the immune system. Some act to destroy or inhibit growth of microbes, e.g. C-reactive protein, Mannose-binding protein, complement factors, ferritin, ceruloplasmin, Serum amyloid A and haptoglobin. Others give negative feedback on the inflammatory response, e.g. serpins. Alpha 2-macroglobulin and coagulation factors affect coagulation.
| Protein | Immune system function |
|---|---|
| C-reactive protein | Opsonin on microbes [1] |
| D-dimer protein | fibrin degradation product |
| Mannose-binding protein | Mannan-binding lectin pathway |
| Alpha 1-antitrypsin | serpin, downregulates inflammation |
| Alpha 1-antichymotrypsin | serpin, downregulates inflammation |
| Alpha 2-macroglobulin |
|
| Fibrinogen, prothrombin, factor VIII, von Willebrand factor, plasminogen | coagulation factors |
| Complement factors | Complement system |
| Ferritin | Binding iron, inhibiting microbe iron uptake |
| Serum amyloid P component (see amyloid) | |
| Serum amyloid A |
|
| Ceruloplasmin | Oxidizes iron, facilitating for ferritin, inhibiting microbe iron uptake |
| Haptoglobin | Bind hemoglobin, inhibiting microbe iron uptake |
[edit] Negative
| Protein | Immune system function of decrease |
|---|---|
| Albumin [3] | |
| Transferrin [3] | |
| Transthyretin [3] | |
| Transcortin | Decreased binding of cortisol, upregulation of inflammation |
| Retinol binding protein |
[edit] Clinical significance
- Further information: Reference_ranges_for_blood_tests#Immunology
Measurement of acute phase proteins, especially C-reactive protein, is a useful marker of inflammation in both medical and veterinary clinical pathology. It correlates with the erythrocyte sedimentation rate (ESR).
They may also indicate liver failure [4]
[edit] References
- ^ Lippincott's Illustrated Reviews: Immunology. Paperback: 384 pages. Publisher: Lippincott Williams & Wilkins; (July 1, 2007). Language: English. ISBN-10: 0781795435. ISBN-13: 978-0781795432. Page 182
- ^ Boer JP, Creasey AA, Chang A, Abbink JJ, et al. (1993) "Alpha-2-macroglobulin functions as an inhibitor of fibrinolytic, clotting, and neutrophilic proteinases in sepsis: studies using a baboon model." Infect Immun. 61(12): 5035–5043.
- ^ a b c Ritchie RF, Palomaki GE, Neveux LM, Navolotskaia O, Ledue TB, Craig WY (1999). "Reference distributions for the negative acute-phase serum proteins, albumin, transferrin and transthyretin: a practical, simple and clinically relevant approach in a large cohort". J. Clin. Lab. Anal. 13 (6): 273-9. PMID 10633294.
- ^ Ananian P, Hardwigsen J, Bernard D, Le Treut YP (2005). "Serum acute-phase protein level as indicator for liver failure after liver resection". Hepatogastroenterology 52 (63): 857-61. PMID 15966220.
[edit] See also
[edit] External links
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