Acute Phase Proteins and their Potential Role as an Indicator for Fish Health and in Diagnosis of Fish Diseases

The acute phase proteins are biochemically and functionally unrelated protein predominantly synthesized in the liver. The local inflammatory cells i.e. macrophages and neutrophils secretes various cytokines like IL-1, IL-6, IL-8 (interleukins) and TNF-α into bloodstream in response to injury and tissue damage, which stimulate hepatocytes to produce protein and release them into the circulation; these proteins are called as acute phase protein (e.g. C-reactive protein (CRP), serum amyloid A (SAA), metal binding protein, lysozyme, lectin, etc.). The acute phase proteins are involved in variety of defence related activities e.g., inactivation of proteolytic enzymes, preventing the distribution of infectious agents (i.e. either by destruction of microorganism or making microbial cell suitable for cell response by modifying surface targets) and restoration of damage tissue and healthy condition. A number of well-known acute phase proteins have disease prognosis importance and change in the APPs level reflects the presence and intensity of inflammation during infection or injury. Further studies are still necessary to develop our knowledge in diagnostic importance of different acute phase proteins in fish and more efforts are needed to differentiate the APPs levels in case of viral, bacterial and parasitic diseases.