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Enhanced oxidative burst in immunologically activated but not elicited polymorphonuclear leukocytes correlates with
Abstract:
Polymorphonuclear neutrophils (PMN) induced locally in immune mice by intraperitoneal injection of antigen exhibit enhanced fungicidal activity compared with PMN elicited with thioglycolate. The mechanism of the differences in these PMN populations was studied. Sublethal infection was used to produce immunity to Blastomyces dermatitidis. A correlation was sought between the ability of PMN to kill, or not kill, B. dermatitidis and the production of the oxidative burst, as measured by luminol-enhanced chemiluminescence (CL). Although elicited PMN cocultured with Candida albicans produced a burst of CL and were candidacidal, killing did not occur when PMN were cocultured with B. dermatitidis. Lack of killing of B. dermatitidis by elicited PMN correlated with lack of stimulation of a brisk oxidative burst. In contrast to elicited PMN, PMN induced by B. dermatitidis antigen responded to this fungus with a burst of CL and a significant reduction of inoculum CFU (80%). Furthermore, these PMN when cocultured with C. albicans produced an enhanced burst of CL, and killing was enhanced compared with that by elicited PMN, e.g., 86 versus 58%. The CL burst and killing of B. dermatitidis by antigen-induced PMN was abrogated in the presence of catalase, implying a critical role for hydrogen peroxide. Partial but significant depression of CL and killing in the presence of dimethyl sulfoxide, a hydroxyl radical scavenger, identified hydroxyl radical, or its metabolites, as a toxic product(s) responsible for a significant fraction of fungicidal activity. These results indicate that the metabolic activity and microbicidal activity of PMN can be altered (enhanced) at the site of an immunological reaction and thus could constitute an important factor in resistance.
Insights
Immune cells called polymorphonuclear neutrophils (PMN) fight fungi better when induced by specific antigens. This enhanced fungicidal activity is linked to a stronger oxidative burst, crucial for combating fungal infections like Blastomyces dermatitidis.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Polymorphonuclear neutrophils (PMN) are key immune cells.
- Thioglycolate elicits PMN with lower fungicidal activity compared to antigen-induced PMN.
- Immunity to Blastomyces dermatitidis can be established via sublethal infection.
Purpose of the Study:
- To investigate the mechanism behind enhanced fungicidal activity of antigen-induced PMN.
- To correlate PMN killing of B. dermatitidis with oxidative burst production.
- To determine the role of reactive oxygen species in PMN fungicidal activity.
Main Methods:
- Comparing PMN elicited by thioglycolate versus those induced by B. dermatitidis antigen.
- Measuring oxidative burst using luminol-enhanced chemiluminescence (CL).
- Assessing PMN fungicidal activity against B. dermatitidis and Candida albicans.
- Using catalase and dimethyl sulfoxide (DMSO) to probe the role of hydrogen peroxide and hydroxyl radicals.
Main Results:
- Antigen-induced PMN showed enhanced killing of B. dermatitidis (80% reduction) and C. albicans (86% vs. 58%) compared to elicited PMN.
- Killing activity correlated with a stronger oxidative burst (CL) in antigen-induced PMN.
- Hydrogen peroxide and hydroxyl radicals were identified as key toxic products mediating fungicidal activity.
Conclusions:
- PMN metabolic and microbicidal activity are enhanced at immunological reaction sites.
- Antigen-specific induction of PMN boosts their fungicidal capacity.
- Reactive oxygen species, particularly hydrogen peroxide and hydroxyl radicals, are critical for PMN-mediated fungal killing.