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Cytochemical demonstration of hydrogen peroxide in polymorphonuclear leukocyte phagosomes
Abstract:
Phagocytosis by polymorphonuclear leukocytes (PMN) is accompanied by specific morphological and metabolic events which may result in the killing of internalized micro-organism. Hydrogen peroxide is produced in increased amounts during phagocytosis (17) and in combination with myeloperoxidase and halide ions constitute a potent, microbicidal mechanism (8,9,11). There can be direct iodination of micro-organisms (10), or alternatively, other intermediate reaction products, i.e. chloramines and aldehydes (21), can exert a microbicidal effect. The H2O2-peroxidase-halide system is presumed to operate within the phagocytic vacuole (12,18). Myeloperoxidase, present in the primary granules of PMN, enters the phagocytic vacuole during degranulation (1,4,7), and halide ions are probably derived from the extracellular medium or are present in the PMN (see 11, 18). For the operation of this system in intact cells, the presence of H2O2 in the phagocytic vacuole is necessary, and indeed this has been suggested by the work of several investigators (12, 18, 21). In the present investigation, the diaminobenzidine reaction of Graham and Karnovsky (5), modified to utilize endogenous myeloperoxidase and hydrogen peroxide, has been applied to actively phagocytizing PMN to demonstrate cytochemically the presence of H2O2 in the phagocytic vacuole.
Insights
Polymorphonuclear leukocytes (PMN) use hydrogen peroxide (H2O2) and myeloperoxidase to kill microbes within phagocytic vacuoles. This study cytochemically confirms H2O2 presence in these vacuoles during phagocytosis.
Area of Science:
- Immunology
- Cell Biology
- Microbiology
Background:
- Phagocytosis by polymorphonuclear leukocytes (PMN) involves metabolic events crucial for microbial killing.
- A key microbicidal mechanism involves hydrogen peroxide (H2O2) in combination with myeloperoxidase and halide ions.
- This H2O2-peroxidase-halide system is believed to function within the phagocytic vacuole.
Purpose of the Study:
- To cytochemically demonstrate the presence of hydrogen peroxide (H2O2) within the phagocytic vacuole of actively phagocytizing PMN.
- To investigate the role of endogenous myeloperoxidase and H2O2 in the microbicidal activity of PMN.
Main Methods:
- Utilized a modified Graham and Karnovsky diaminobenzidine reaction.
- Employed endogenous myeloperoxidase and hydrogen peroxide for cytochemical staining.
- Applied the method to actively phagocytizing PMN to visualize H2O2 localization.
Main Results:
- Successfully demonstrated the presence of hydrogen peroxide (H2O2) within the phagocytic vacuole.
- Provided cytochemical evidence supporting the operation of the H2O2-peroxidase-halide microbicidal system within phagocytic vacuoles.
- Confirmed the necessity of H2O2 in the phagocytic vacuole for effective microbial killing by PMN.
Conclusions:
- Hydrogen peroxide (H2O2) is demonstrably present in the phagocytic vacuole during PMN phagocytosis.
- This finding supports the proposed H2O2-peroxidase-halide microbicidal mechanism operating intracellularly.
- The study provides cytochemical evidence for a critical component of the innate immune response in PMN.