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Mycoplasma pneumoniae induces cytotoxic activity in guinea pig bronchoalveolar cells
Abstract:
Precultured guinea pig alveolar macrophages (AM) and freshly harvested alveolar cells (FHAC) activated by interaction with Mycoplasma pneumoniae were cytotoxic for xenogeneic 75selenomethionine-labeled tumor target cells. Phagocytosis of whole opsonized or nonopsonized M. pneumoniae cells was more effective in eliciting cytotoxicity than uptake of sonicated microorganisms. The addition of living mycoplasma cells to the assay system enhanced the cytotoxic effect considerably. Target cells were significantly more susceptible to the cytotoxic action of phagocytes if they were coated with mycoplasma antigen or cocultured together with M. pneumoniae. The activation of the phagocytes could be inhibited by 2-deoxy-D-glucose but not by antimicrobial substances suppressing mycoplasma protein synthesis. It was accompanied by 51Cr release without detectable signs of cell damage. The supernatants of activated cells were cytotoxic for approximately 24 h. Inhibition, release, and cytotoxic activity indicate the necessity of an intact metabolism of the effector cells and suggest a secretion of cytotoxic substances.
Insights
Guinea pig alveolar macrophages (AM) and alveolar cells activated by Mycoplasma pneumoniae showed cytotoxicity against tumor cells. This immune response was enhanced by whole M. pneumoniae cells and mycoplasma antigens.
Area of Science:
- Immunology
- Microbiology
Background:
- Alveolar macrophages (AM) play a crucial role in lung immunity.
- Mycoplasma pneumoniae is a common respiratory pathogen.
- Understanding host-pathogen interactions is vital for developing therapeutic strategies.
Purpose of the Study:
- To investigate the cytotoxic effects of activated alveolar macrophages and alveolar cells against tumor target cells.
- To determine the role of Mycoplasma pneumoniae in modulating this cytotoxic activity.
- To elucidate the mechanisms underlying phagocyte activation and cytotoxicity.
Main Methods:
- Activation of guinea pig AM and freshly harvested alveolar cells (FHAC) through interaction with M. pneumoniae.
- Assessment of cytotoxicity against 75selenomethionine-labeled xenogeneic tumor target cells.
- Evaluation of the impact of whole vs. sonicated M. pneumoniae, living mycoplasma cells, and mycoplasma antigens on phagocyte activation.
Main Results:
- Activated AM and FHAC exhibited significant cytotoxicity towards tumor target cells.
- Phagocytosis of whole M. pneumoniae cells was more effective than sonicated forms in inducing cytotoxicity.
- Co-culture with living M. pneumoniae or exposure to mycoplasma antigens enhanced target cell susceptibility.
- Phagocyte activation was inhibited by 2-deoxy-D-glucose, suggesting an energy-dependent process, and was associated with 51Cr release without cell damage.
- Supernatants from activated cells retained cytotoxic activity for up to 24 hours.
Conclusions:
- Mycoplasma pneumoniae can activate alveolar phagocytes to become cytotoxic against tumor cells.
- The cytotoxic mechanism involves the secretion of soluble factors dependent on intact effector cell metabolism.
- These findings highlight a novel immunomodulatory role of M. pneumoniae in the context of cellular cytotoxicity.