Acute phase proteins

• The acute phase response (APR) is a non-specific inflammatory reaction that develops shortly after tissue damage (infection, immunological, neoplasia, trauma, and parasitic conditions). Despite its name, the acute phase response accompanies both acute and chronic inflammatory states.
• The acute-phase response includes changes in concentration of plasma proteins called acute phase proteins (APPs). APPs can be divided into two groups:
  • Positive APPs (glycoproteins synthesized and released predominantly by hepatocytes in response to pro-inflammatory cytokines) and
  • Negative APPs (proteins whose concentration reduces in acute inflammation usually due to reduced hepatocyte synthesis).
• Most animals have the same acute phase proteins, although the magnitude of response varies between species.
• The positive APPs in dogs and cats can be further classified by the magnitude of the increase in their plasma concentration in response to stimuli into major APPs (10-100 fold increase), and moderate APPs (2-10 fold increase).
• In cats alpha-1 acid glycoprotein (AGP) and serum amyloid A (SAA) are major APPs, haptoglobin (Hp) is a moderate APP.
• Acute phase proteins are extremely sensitive but non-specific markers of inflammation. An increase in circulating concentrations of APPs is 6-14 times more sensitive a marker of inflammation than is an increase in leucocyte count.
• All APPs are measured in serum samples.
• Concentrations of SAA, AGP and Hp are higher in older cats and slightly higher in female versus male cats. Abyssinian Abyssinian cats are predisposed to amyloidosis Amyloidosis and concentrations of SAA have been shown to be slightly higher in Abyssinian cats than in other breeds of cats. Concentrations of SAA do not appear to differ between Abyssinian cats with amyloidosis and those without. These variations are unlikely to have a significant effect on interpretation of results in a clinical setting.

Acute phase proteins as a diagnostic test

Examples of the use of APPs in clinical practice

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Tamamoto T, Ohno K, Takahashi M et al (2013) Serum amyloid A as a prognostic marker in cats with various diseases. J Vet Diagn Invest 25 (3), 428-32 PubMed.
• Tamamoto T, Ohno K, Ohmi A et al (2008) Verification of measurement of the feline serum amyloid A (SAA) concentration by human SAA turbidimetric immunoassay and its clinical application. J Vet Med Sci 70 (11), 1247-1252 PubMed.
• Ceron J J, Eckersall P D & Martýnez-Subiela S (2005) Acute phase proteins in dogs and cats: current knowledge and future perspectives. Vet Clin Pathol 34 (2), 85-99 PubMed.
• Paltrinieri S, Giordano A & Tranquillo V (2005) Role of Alpha-1-Acid Glycoprotein for Diagnosing Feline Infectious Peritonitis (FIP). Vet Clin Pathol 34 (Suppl), 295.

Other sources of information

• Winkel V M, Hora A S, Brandao P E & Lucas S R R (2013) Alpha-1-Acid Glycoprotein Concentrations in Cats with Feline Infectious Peritonitis. ACVIM Proceedings.
• Bell R & Eckersall D (2008) Laboratory updates: Acute phase protein tests for diagnosis and monitoring of disease in small animals. UK Vet 13, 1-4.
• Tecles F, Martínez Subiela S, Parra M D, Spiranelli E, Paltrinieri S, Cerón J J (2004) Use of Acute Phase Proteins for Monitoring Treatment Evolution in Dogs with Different Pathologic Conditions.14th ECVIM-CA Congress.