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🛡️immunobiology review

Myeloperoxidase

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

Myeloperoxidase (MPO) is an enzyme found primarily in neutrophils and monocytes, crucial for the innate immune response. This enzyme plays a significant role in generating reactive oxygen species during the respiratory burst, which helps kill pathogens. By converting hydrogen peroxide into hypochlorous acid, myeloperoxidase acts as a potent antimicrobial agent that contributes to the body's first line of defense against infections.

5 Must Know Facts For Your Next Test

  1. Myeloperoxidase is stored in the azurophilic granules of neutrophils and is released upon activation during an immune response.
  2. The enzyme is not only involved in pathogen destruction but also plays a role in tissue damage during inflammation.
  3. MPO levels can be measured in blood and are often used as a biomarker for various inflammatory conditions and cardiovascular diseases.
  4. Deficiency in myeloperoxidase can lead to increased susceptibility to infections due to impaired microbial killing.
  5. Myeloperoxidase can also contribute to oxidative stress, which is linked to various chronic diseases when produced in excess.

Review Questions

  • How does myeloperoxidase contribute to the innate immune response during an infection?
    • Myeloperoxidase contributes to the innate immune response primarily through its ability to generate hypochlorous acid from hydrogen peroxide. When neutrophils encounter pathogens, they undergo a respiratory burst that increases reactive oxygen species, facilitating the production of MPO. This enzyme then catalyzes the conversion of hydrogen peroxide into hypochlorous acid, which effectively kills bacteria and fungi, helping to clear infections.
  • Discuss the clinical significance of measuring myeloperoxidase levels in patients.
    • Measuring myeloperoxidase levels in patients has significant clinical implications as elevated MPO levels are associated with various inflammatory conditions, including cardiovascular diseases. High levels can indicate ongoing inflammation and tissue damage, making it a valuable biomarker for assessing the risk of heart disease or monitoring inflammatory disorders. Conversely, low levels may suggest impaired immune function and increased susceptibility to infections.
  • Evaluate how deficiencies in myeloperoxidase might affect an individual's overall health and immune function.
    • Deficiencies in myeloperoxidase can have serious implications for an individual's health by compromising the innate immune system's ability to kill pathogens effectively. This can lead to recurrent infections, particularly with bacterial organisms that MPO would typically help eliminate. Additionally, these individuals may experience increased inflammation or tissue damage since without adequate MPO activity, other compensatory mechanisms might fail to manage oxidative stress effectively, potentially resulting in chronic inflammatory conditions.