Acute Response In Animals

Comparative Medicine Copyright 2009 by the American Association for Laboratory Animal Science

Vol 59, No 6 December 2009 Pages 517–526

Acute Phase Response in Animals: A Review
Carolyn Cray,1,* Julia Zaias,1,2 and Norman H Altman1 The acute phase response is a complex systemic early-defense system activated by trauma, infection, stress, neoplasia, and inflammation. Although nonspecific, itserves as a core of the innate immune response involving physical and molecular barriers and responses that serve to prevent infection, clear potential pathogens, initiate inflammatory processes, and contribute to resolution and the healing process. Acute phase proteins, an integral part of the acute phase response, have been a focus of many applications in human diagnostic medicine and recentlyhave been identified in common animal species. Potential applications to diagnosis, prognosis, assessment of animal health, and laboratory animal welfare are readily apparent. Abbreviations: APP, acute phase protein; APR, acute phase response; CRP, C reactive protein; SAA, serum amyloid A.

Acute phase proteins (APP) are blood proteins primarily synthesized by hepatocytes as part of the acutephase response (APR). The APR is part of the early-defense or innate immune system, which is triggered by different stimuli including trauma, infection, stress, neoplasia, and inflammation. The APR results in a complex systemic reaction with the goal of reestablishing homeostasis and promoting healing. The APR has been referred to as the ‘molecular thermometer’ whereby quantitation of individual APPcan provide an assessment of the response to the triggering event.10,82,93 APP have been well recognized for their application to human diagnostic medicine and have been described to have value in the diagnosis and prognosis of cardiovascular disease, autoimmunity, organ transplant, and cancer treatment.15,16,24,36,50,57,73, 102 C-reactive protein (CRP) was the first APP described (in the early1930s), and its presence early during pneumococcal infection of monkeys and humans thereby led to the coinage of ‘acute phase’ term.1,123 Today, CRP remains an APP of primary interest in humans, where it is a major marker of infection, autoimmune disease, trauma, malignancy, and necrosis including myocardial infarction.92 Furthermore, CRP has been proposed as a marker for wellness assessments,which is a common role proposed in many studies of human and animal APP.73 Although the study of serum proteins in animals was commonly conducted in research investigations in the mid-1900s, the wider application of APP in veterinary medicine was not reported until the early 1990s. Several review papers with descriptions of APP and APR in companion animals and rodents are available.10,39,82,93 Likehuman APP, animal APP have been well documented to be sensitive to similar triggering events. In large animals, APP have been further proposed as markers of ‘herd health.’40,82,93 In companion animals, APP have especially been identified for prognostic applications.10 The use of APP in laboratory animals has essentially been limited to research based investigations, but APP have been proposed as anobjective marker
Received: 27 Jul 2009. Revision requested: 23 Aug 2009. Accepted: 05 Sep 2009. 1 Division of Comparative Pathology and 2Division of Veterinary Resources, University of Miami Miller School of Medicine, Miami, Florida. * Corresponding author. Email: c.cray@miami.edu

for humane experimental endpoints.39,89 The following sections summarize the biologic effects of the APR, currentissues and options in the quantitation of APP and APR, applications of APP in the diagnosis and prognosis of disease in animal species, and proposed applications of APP in laboratory animals.

Innate immunity fulfills an important role in the body’s early defense mechanism and serves to initiate the acquired immune response. The innate immune system is very diverse and includes physical...