Serum amyloid A in equine health and disease

Abstract

Serum amyloid A (SAA) is the major acute phase protein in horses. It is produced during the acute phase response (APR), a nonspecific systemic reaction to any type of tissue injury. In the blood of healthy horses, SAA concentration is very low, but it increases dramatically with inflammation. Due to the short half-life of SAA, changes in its concentration in blood closely reflect the onset of inflammation and, therefore, measurement of SAA useful in the diagnosis and monitoring of disease and response to treatment. Increases in SAA concentration have been described in equine digestive, reproductive and respiratory diseases and following surgical procedures. Moreover, SAA has proven useful for detection of some subclinical pathologies that can disturb training and competing in equine athletes. Increasing availability of diagnostic tests for both laboratory and field use adds to SAA's applicability as a reliable indicator of horses' health status. This review article presents the current information on changes in SAA concentrations in the blood of healthy and diseased horses, focussing on clinical application of this biomarker.

Keywords: SAA; acute phase proteins; acute phase reaction; horse; inflammatory diseases.

Figure 1

Serum amyloid A (SAA) as a multifunctional protein in modulating the inflammatory response. IL‐6 produced by macrophages after local stimulation promotes the hepatic production of SAA which has roles in inhibition of lymphocyte proliferation, neutrophil activities, adhesion of T lymphocytes to extracellular matrix, platelet aggregation and induction of adhesion, migration and tissue infiltration of monocytes, neutrophils and prostaglandin synthesis (This figure was prepared using Servier Medical Art. https://smart.servier.com/).