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Uptake and degradation of Pneumocystis carinii by macrophages in vitro
Abstract:
Pneumocystis carinii organisms, isolated from lungs of rats with glucocorticoid-induced pneumocystosis, were ingested and degraded in vitro by alveolar and peritoneal macrophages obtained from healthy rats and mice. Uptake of the organisms was inhibited at 4 degrees C and by treatment of macrophages with iodoacetate. Neither uptake nor degradation was inhibited by pretreatment of macrophages with hydrocortisone sodium phosphate in vitro. Although peritoneal macrophages of any age in vitro were capable of ingesting Pneumocystis, alveolar macrophages that had been cultivated in vitro for less than 2 days were incapable of phagocytosis of the organism, a functional defect that corrected itself spontaneously during cultivation in vitro.
Insights
Macrophages can engulf and break down Pneumocystis carinii organisms. Alveolar macrophages showed a temporary inability to phagocytose these fungi, which resolved with in vitro cultivation.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Pneumocystis carinii causes opportunistic infections, particularly in immunocompromised individuals.
- Macrophage phagocytosis is a critical immune defense mechanism against microbial pathogens.
Purpose of the Study:
- To investigate the in vitro phagocytic and degradative capabilities of macrophages against Pneumocystis carinii.
- To determine the effects of temperature, metabolic inhibitors, and glucocorticoids on macrophage-host-pathogen interactions.
Main Methods:
- Isolation of Pneumocystis carinii organisms from glucocorticoid-induced rat pneumocystosis models.
- In vitro incubation of organisms with alveolar and peritoneal macrophages from rats and mice.
- Assessment of phagocytosis and degradation using various experimental conditions (temperature, metabolic inhibitors, hydrocortisone).
Main Results:
- Both alveolar and peritoneal macrophages ingested and degraded Pneumocystis carinii in vitro.
- Phagocytosis was reduced at 4°C and inhibited by iodoacetate, indicating an energy-dependent process.
- Hydrocortisone sodium phosphate pretreatment did not affect uptake or degradation.
- Newly isolated alveolar macrophages exhibited a transient phagocytic defect, which was restored upon in vitro cultivation.
Conclusions:
- Macrophages play a role in controlling Pneumocystis carinii infections through phagocytosis and degradation.
- Alveolar macrophage phagocytic function against Pneumocystis carinii can be temporarily impaired but recovers with in vitro culture.