The interaction in vitro of Pneumocystis carinii with macrophages and L-cells
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Abstract:
A model was developed for studying the interaction between Pneumocystis, rat-derived cells, and humoral factors. Pneumocystis were obtained in large quantity by bronchial lavage of steroid-treated rats. The trophozoite was the predominant form obtained, and it could readily be recognized by phase contrast microscopy. Organisms maintained a typical morphology for at least 3 days in culture, and 10-20% took up radiolabeled nucleotides. Pneumocystis readily adhered to cell surfaces in a similar manner in alveolar macrophages from steroid-treated or normal rats, mouse peritoneal macrophages, and L-cells. Adherent organisms were not interiorized to a significant degree in the absence of antipneumocystis serum. After addition of rabbit antipneumocystis serum, rapid interiorization of organisms occurred from the surface of macrophages but not L-cells. Organisms appeared to be promptly destroyed within macrophages after interiorization. Persisting or multiplying intracellular forms were not seen. Antipneumocystis serum did not morphologically alter Pneumocystis. These observations suggest a role for antibody and mononuclear phagocytes during the immune response to Pneumocystis.
Insights
Antibody and mononuclear phagocytes are crucial for controlling Pneumocystis infection. This study shows that immune serum and macrophages effectively clear Pneumocystis, preventing its proliferation.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Pneumocystis is an opportunistic pathogen causing pneumonia, particularly in immunocompromised individuals.
- Understanding the host-pathogen interaction is vital for developing effective treatments.
Purpose of the Study:
- To develop a model for studying Pneumocystis interactions with host cells and immune factors.
- To investigate the role of humoral factors and phagocytes in Pneumocystis clearance.
Main Methods:
- Large-scale isolation of Pneumocystis trophozoites via bronchial lavage of rats.
- In vitro cell adhesion assays using rat alveolar macrophages, mouse peritoneal macrophages, and L-cells.
- Assessment of organism interiorization and destruction following addition of antipneumocystis serum.
Main Results:
- Pneumocystis adhered to various cell types, with significant interiorization by macrophages only after addition of antipneumocystis serum.
- Internalized Pneumocystis was rapidly destroyed within macrophages; no intracellular persistence or multiplication was observed.
- Antipneumocystis serum did not cause direct morphological changes to Pneumocystis organisms.
Conclusions:
- Antibody, in conjunction with mononuclear phagocytes, plays a critical role in the immune response to Pneumocystis.
- This model provides insights into the mechanisms of Pneumocystis clearance by the host immune system.