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Updated: May 13, 2026
Bone Marrow-derived Macrophage Production
Published on: November 22, 2013
Intracellular localization of myeloperoxidase in murine peritoneal B-lymphocytes and macrophages
Tomaz Henrique de Araujo1, Sabrina Sayori Okada, Eliver Eid Bou Ghosn
1Instituto de Ciências Biomédicas, Universidade Federal de Alfenas, Alfenas, MG 37130, Brazil.
Abstract:
Generation of hypochlorous acid (HOCl), an important microbicidal agent, is considered to be the main function of myeloperoxidase (MPO), an enzyme present in phagocytes. High amounts of MPO are present in neutrophil azurophilic granules, which are mobilized into the phagolysosome vacuole during phagocytosis. MPO is also present in monocytes and macrophages, although to a lesser degree than in neutrophils. In the present study, we investigated the distribution of MPO in murine peritoneal cells using flow cytometry, confocal microscopy (CM) and transmission electron microscopy (TEM). MPO was observed in macrophages, and surprisingly, we detected MPO in B lymphocytes, specifically in B1-a. MPO was present in cytoplasmic granules, vesicles, mitochondria and the nucleus of murine peritoneal cells. Together, these findings suggest that, in addition to its known microbicidal activity, MPO has a myriad of other unanticipated cellular functions.
Insights
Myeloperoxidase (MPO) is crucial for generating hypochlorous acid (HOCl) in phagocytes. This study surprisingly found MPO in B lymphocytes and various cellular compartments, suggesting novel functions beyond microbial defense.
Area of Science:
- Immunology
- Cell Biology
Background:
- Myeloperoxidase (MPO) is a key enzyme in phagocytes, primarily known for generating hypochlorous acid (HOCl) for microbial killing.
- MPO is abundant in neutrophils and present in monocytes and macrophages, playing a role in innate immunity.
Purpose of the Study:
- To investigate the distribution of MPO within murine peritoneal cells.
- To identify novel cellular locations and potential functions of MPO.
Main Methods:
- Flow cytometry was used to analyze MPO distribution.
- Confocal microscopy (CM) and transmission electron microscopy (TEM) provided high-resolution imaging of MPO localization.
Main Results:
- MPO was confirmed in macrophages.
- Unexpectedly, MPO was detected in B lymphocytes, particularly B1-a cells.
- MPO was found in cytoplasmic granules, vesicles, mitochondria, and the nucleus of peritoneal cells.
Conclusions:
- MPO exhibits a broader cellular distribution than previously understood.
- The presence of MPO in diverse cellular compartments suggests uncharacterized functions beyond its microbicidal role.
