ACUTE-PHASE PROTEINS AS MARKERS OF INFLAMMATORY LESIONS

Acute phase proteins are liver-derived serum proteins, the concentration of which alters in response to infection or inflammation. Cytokines such as interleukin-6, interleukin-1 and tumour necrosis factor-alpha stimulate the liver to produce haptoglobin (Hp), serum amyloid A (SAA), C-reactive protein (CRP), alpha(1)-acid glycoprotein (AGP) and fibrinogen (Fb) but limit the production of negative acute phase proteins such as albumin. There are interspecies variations in the pattern of response of the acute phase proteins but they are valuable as markers of inflammatory lesions providing diagnostic information for veterinary medicine. Advances have been made in the study of acute phase protein in pigs, dogs and cattle. In the pig, it is evident that CRP is a major reactant whereas Hp is a moderate acute phase reactant. The use of CRP for the diagnosis of inflammatory disease in dogs has been confirmed with studies relating the canine serum CRP concentration to haematological determination of inflammation. CRP assay in canine serum has been shown to confirm primary infectious or inflammatory conditions but can also detect secondary conditions where the primary condition is non-inflammatory. In cattle, the use of Hp assay is now established as a major aid to the diagnosis of infectious and inflammatory disease. Additional benefit to the diagnosis of disease can be provided by analysis of a profile of acute phase proteins such as a combined analysis of SAA, Hp and AGP. The circulating concentration of AGP is maintained at an increased level for a more extended period than that of SAA or Hp in chronic inflammatory conditions. A major advance would be made in the analysis of animal acute phase protein if internationally recognised standards of the proteins in each species were to become available.