Acute-phase reaction

Acute-phase reaction is a complex physiological response to inflammation, infection, trauma, and certain other stimuli, where the liver rapidly produces a group of proteins known as acute-phase proteins. This response is part of the innate immune system, acting to restore homeostasis, limit infection, and initiate repair processes.

Overview

The acute-phase reaction is characterized by significant changes in the concentrations of certain plasma proteins, termed acute-phase proteins. These proteins include C-reactive protein (CRP), fibrinogen, serum amyloid A (SAA), and mannose-binding lectin (MBL), among others. The levels of these proteins can increase or decrease by at least 25% during an acute-phase reaction. The increase in acute-phase proteins serves various functions, including the enhancement of phagocytosis, neutralization of enzymes and toxins, and modulation of the immune response.

Mechanism

The acute-phase reaction is primarily mediated by cytokines, such as interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α), which are released by macrophages and other cells in response to infection, injury, or immune disturbances. These cytokines signal the liver to produce and secrete acute-phase proteins. The extent and duration of the acute-phase reaction can vary depending on the severity and type of the triggering event.

Clinical Significance

The measurement of acute-phase proteins, particularly CRP, is a useful diagnostic tool in clinical practice. Elevated levels of CRP and other acute-phase proteins can indicate the presence of inflammation, infection, or other pathological conditions. However, these markers are not specific to any single disease, so they must be interpreted in the context of the patient's overall clinical picture.

Acute-phase proteins also have prognostic value in various diseases, including cardiovascular disease, where elevated CRP levels have been associated with an increased risk of heart attacks, stroke, and other cardiovascular events.

Treatment and Management

The management of an acute-phase reaction focuses on treating the underlying cause of the inflammation or infection. This may involve the use of antibiotics, anti-inflammatory drugs, or other therapeutic interventions. In some cases, specific measures to reduce the levels of acute-phase proteins may be warranted, although this is not typically the primary focus of treatment.

Conclusion

The acute-phase reaction is a vital component of the body's defense mechanism, playing a crucial role in the early stages of the immune response. Understanding the dynamics of acute-phase proteins can aid in the diagnosis, management, and prognosis of various diseases.