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Superoxide production by phagocytic leukocytes
Abstract:
Mononuclear phagocytic leukocytes, as well as polymorphonuclear leukocytes, produce and release superoxide at rest, and this is stimulated by phagocytosis. Of the mouse monocytic cells studied, alveolar macrophages released the largest amounts of superoxide during phagocytosis, followed by normal peritoneal macrophages. Casein-elicited and "activated" macrophages released smaller quantities. In the guinea pig, polymorphonuclear leukocytes and casein-elicited macrophages were shown to release superoxide during phagocytosis whereas alveolar macrophages did not. Superoxide release accounted for only a small fraction of the respiratory burst of phagocytosis in all but the normal mouse peritoneal macrophage, the guinea pig polymorphonuclear leukocyte, and probably the mouse alveolar macrophage. There are obviously considerable species differences in O2-release by various leukocytes that might reflect both the production and/or destruction (e.g. by dismutase) of that substance.
Insights
Leukocytes release superoxide during phagocytosis, with significant species differences observed. Mouse alveolar macrophages and guinea pig neutrophils showed the most superoxide release, impacting the respiratory burst.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Leukocytes, including mononuclear phagocytes and polymorphonuclear leukocytes, generate superoxide at rest.
- Phagocytosis significantly stimulates superoxide release in these cells.
- Species-specific variations in superoxide production and release are known to exist.
Purpose of the Study:
- To investigate and compare superoxide release from different types of leukocytes across species during phagocytosis.
- To determine the contribution of superoxide release to the overall respiratory burst in various leukocyte populations.
Main Methods:
- Comparative analysis of superoxide release from mouse and guinea pig leukocytes.
- Measurement of superoxide production in resting and phagocytosing alveolar macrophages, peritoneal macrophages, and polymorphonuclear leukocytes.
- Assessment of superoxide's role in the respiratory burst.
Main Results:
- Mouse alveolar macrophages and normal peritoneal macrophages released substantial superoxide during phagocytosis, unlike casein-elicited or activated macrophages.
- Guinea pig polymorphonuclear leukocytes and casein-elicited macrophages released superoxide, but guinea pig alveolar macrophages did not.
- Superoxide release constituted a minor part of the respiratory burst in most tested leukocytes, with notable exceptions.
Conclusions:
- Significant species and cell-type-specific differences exist in leukocyte superoxide release during phagocytosis.
- Superoxide production is a component of the respiratory burst, but its relative contribution varies considerably.
- Mechanisms regulating superoxide production and degradation (e.g., superoxide dismutase) likely account for observed interspecies variations.