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Acute phase protein

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<!-- start content -->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).

Inflammatory cells and red blood cells

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.
<TABLE class=wikitable><CAPTION>"Positive" acute phase proteins:</CAPTION><TBODY><TR><TH>Protein</TH><TH>Immune system function</TH></TR><TR><TH>C-reactive protein</TH><TD>Opsonin on microbes <SUP class=reference id=cite_ref-Immunology182_0-0>[1]</SUP></TD></TR><TR><TH>D-dimer protein</TH><TD>fibrin degradation product</TD></TR><TR><TH>Mannose-binding protein</TH><TD>Mannan-binding lectin pathway</TD></TR><TR><TH>Alpha 1-antitrypsin</TH><TD>serpin, downregulates inflammation</TD></TR><TR><TH>Alpha 1-antichymotrypsin</TH><TD>serpin, downregulates inflammation</TD></TR><TR><TH>Alpha 2-macroglobulin</TH><TD></TD></TR><TR><TH>Fibrinogen, prothrombin, factor VIII, von Willebrand factor, plasminogen</TH><TD>coagulation factors</TD></TR><TR><TH>Complement factors</TH><TD>Complement system</TD></TR><TR><TH>Ferritin</TH><TD>Binding iron, inhibiting microbe iron uptake</TD></TR><TR><TH>Serum amyloid P component (see amyloid)</TH><TD></TD></TR><TR><TH>Serum amyloid A</TH><TD></TD></TR><TR><TH>Ceruloplasmin</TH><TD>Oxidizes iron, facilitating for ferritin, inhibiting microbe iron uptake</TD></TR><TR><TH>Haptoglobin</TH><TD>Bind hemoglobin, inhibiting microbe iron uptake</TD></TR></TBODY></TABLE>
[edit] Negative

<TABLE class=wikitable><CAPTION>"Negative" acute phase proteins:</CAPTION><TBODY><TR><TH>Protein</TH><TH>Immune system function of decrease</TH></TR><TR><TH>Albumin <SUP class=reference id=cite_ref-Ritchie_2-0>[3]</SUP></TH><TD></TD></TR><TR><TH>Transferrin <SUP class=reference id=cite_ref-Ritchie_2-1>[3]</SUP></TH><TD></TD></TR><TR><TH>Transthyretin <SUP class=reference id=cite_ref-Ritchie_2-2>[3]</SUP></TH><TD></TD></TR><TR><TH>Transcortin</TH><TD>Decreased binding of cortisol, upregulation of inflammation</TD></TR><TR><TH>Retinol binding protein</TH><TD></TD></TR></TBODY></TABLE>
[edit] Clinical significance

<DL><DD>Further information: Reference_ranges_for_blood_tests#Immunology </DD></DL>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 <SUP class=reference id=cite_ref-3>[4]</SUP>

[edit] References

  1. <LI id=cite_note-Immunology182-0>^ 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 <LI id=cite_note-1>^ 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. <LI id=cite_note-Ritchie-2>^ <SUP>a</SUP> <SUP>b</SUP> <SUP>c</SUP> <CITE style="FONT-STYLE: normal">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.</CITE>
  2. ^ <CITE style="FONT-STYLE: normal">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.</CITE>