Acute Phase Response

Definition

The acute phase response is a rapid, systemic, and nonspecific reaction of the body to various forms of inflammation, infection, tissue damage, or other stressors. It is a coordinated series of physiological and biochemical changes that occur to help the body combat the underlying cause of the disturbance and restore homeostasis.

5 Must Know Facts For Your Next Test

1. The acute phase response is a key part of the body's innate immune defense system, helping to fight infection and promote healing.
2. Cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), are the primary mediators that trigger the acute phase response.
3. Acute-phase proteins, like C-reactive protein (CRP) and serum amyloid A (SAA), are produced by the liver and help neutralize pathogens, activate the complement system, and facilitate tissue repair.
4. The acute phase response leads to physiological changes, such as fever, increased heart rate, and altered hormone levels, to support the body's defense mechanisms.
5. Prolonged or excessive acute phase response can contribute to the development of chronic inflammatory diseases, such as rheumatoid arthritis and cardiovascular disease.

Review Questions

• Explain how the acute phase response is triggered and the role of cytokines in this process.
  • The acute phase response is triggered by the release of cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), in response to various stimuli, including infection, tissue damage, or inflammation. These cytokines act as signaling molecules, alerting the body to the presence of a disturbance and initiating a coordinated series of physiological and biochemical changes to combat the underlying cause and restore homeostasis. The cytokines stimulate the liver to produce acute-phase proteins, which play a crucial role in the body's defense mechanisms.
• Describe the role of acute-phase proteins in the acute phase response and their contribution to the body's immune defenses.
  • Acute-phase proteins, such as C-reactive protein (CRP) and serum amyloid A (SAA), are produced by the liver in response to cytokine signals during the acute phase response. These proteins help combat infection, neutralize pathogens, and promote tissue repair. CRP, for example, can activate the complement system, which helps destroy invading microorganisms, while SAA can bind to and neutralize bacteria and viruses. Additionally, acute-phase proteins can enhance phagocytosis, the process by which immune cells engulf and destroy foreign or damaged cells. By contributing to these various immune functions, acute-phase proteins play a vital role in the body's defense against threats and in the restoration of homeostasis.
• Analyze the potential consequences of a prolonged or excessive acute phase response and its link to the development of chronic inflammatory diseases.
  • While the acute phase response is a crucial part of the body's innate immune defense system, a prolonged or excessive response can have negative consequences. Sustained high levels of cytokines and acute-phase proteins can lead to chronic inflammation, which has been linked to the development of various chronic diseases, such as rheumatoid arthritis, cardiovascular disease, and metabolic disorders. The persistent inflammation can damage healthy tissues and disrupt normal physiological processes. For example, elevated C-reactive protein levels have been associated with an increased risk of heart disease, as the inflammation can contribute to the buildup of plaque in the arteries. Understanding the potential consequences of an unregulated acute phase response is important for identifying and managing chronic inflammatory conditions.

Related terms

Cytokines:

Small signaling proteins secreted by various cells, including immune cells, that play a crucial role in initiating and regulating the acute phase response.

Acute-Phase Proteins: Proteins synthesized by the liver in response to cytokine signals during the acute phase response, which help combat infection, neutralize pathogens, and promote tissue repair.

Inflammation:

The body's protective immune response to harmful stimuli, such as pathogens, damaged cells, or irritants, which triggers the acute phase response.