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In vivo interaction between alveolar macrophages and Cryptococcus neoformans
K Nessa1, N T Gross, C Jarstrand
1Division of Inhalation Toxicology, Karollnska Institute, Stockholm, Sweden.
Abstract:
In vivo interactions of rabbit alveolar macrophages (AM) and Cryptococcus neoformans, a yeast pathogenic for humans, were studied. As a control, inert silica particles of a similar diameter (5-6 microns) were used. Of 16 rabbits, 6 were instilled intratracheally with fluorescein-labelled heat-killed C. neoformans, 6 with fluorescein-labelled silica particles and 4 with saline only. After 24 h, the AM were collected by lung lavage, and phagocytosis, oxidative metabolism, phagolysosomal pH and morphology were studied. The accumulated number of yeasts attached to the AM was almost the same for C. neoformans as for the silica particles. The ingested fraction of C. neoformans was even higher than that of the silica particles. Quantitative NBT reduction by the AM, reflecting their oxidative metabolism, was markedly increased by exposure to C. neoformans for 24 h. The phagolysosomal pH was on the average lower in phagolysosomes with C. neoformans than with the silica particles, although approximately 2% of the phagolysosomes with C. neoformans had neutral pH. Phagolysosomes with neutral pH was not observed for silica particles. Electron microscopy showed presence of C. neoformans in phagolysosomes of AM. The conclusion of this study is that the phagocytic activity, oxidative metabolism and phagolysosomal pH AM against C. neoformans are significant 24 h after the exposure.
Insights
Rabbit alveolar macrophages (AM) actively engulf Cryptococcus neoformans, showing increased oxidative metabolism and lower phagolysosomal pH. These immune responses are significant 24 hours post-exposure to the pathogenic yeast.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Cryptococcus neoformans is a significant human pathogen.
- Alveolar macrophages (AM) are key immune cells in the lung.
- Understanding host-pathogen interactions is crucial for developing treatments.
Purpose of the Study:
- To investigate the in vivo interaction between rabbit alveolar macrophages and Cryptococcus neoformans.
- To compare the macrophage response to C. neoformans with that to inert silica particles.
Main Methods:
- Rabbits were intratracheally instilled with labeled C. neoformans or silica particles.
- Alveolar macrophages were collected via lung lavage after 24 hours.
- Phagocytosis, oxidative metabolism (NBT reduction), phagolysosomal pH, and morphology were analyzed.
Main Results:
- AM showed similar attachment of C. neoformans and silica particles, but higher ingestion of yeast.
- Quantitative NBT reduction by AM significantly increased after C. neoformans exposure.
- Phagolysosomal pH was generally lower with C. neoformans compared to silica, with some yeast-containing phagolysosomes showing neutral pH.
Conclusions:
- Rabbit alveolar macrophages exhibit significant phagocytic activity against C. neoformans.
- Exposure to C. neoformans markedly enhances AM oxidative metabolism.
- The phagolysosomal pH environment within AM plays a role in controlling C. neoformans infection.