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Interaction of Chlamydia psittaci reticulate bodies with mouse peritoneal macrophages
Abstract:
Noninfectious reticulate bodies of Chlamydia psittaci are readily phagocytized by thioglycolate-elicited mouse peritoneal macrophages in monolayer culture. The internalized reticulate bodies are rapidly destroyed as indicated by a 60 to 70% decrease in trichloroacetic acid-precipitable radioisotopic counts in the macrophage pellet by 10 h and a concomitant increase of the trichloroacetic acid-soluble radiolabeled chlamydial nucleic acid in the cytoplasm. This intracellular destruction of reticulate bodies in macrophages is independent of the multiplicity of infection. Reticulate bodies at a high multiplicity of infection, up to 1,000:1, are also incapable of inducing immediate cytotoxicity in macrophages as evidenced by the lack of early release of the host cell-soluble cytoplasmic enzyme lactic dehydrogenase. Thus, it appears that the virulence factors for (i) initiation or maintenance of intracellular survival via circumvention of phagolysosome formation and (ii) host cell damage are either missing or not expressed by the RB form of this bacterium.
Insights
Noninfectious Chlamydia psittaci reticulate bodies are phagocytized and rapidly destroyed by mouse macrophages. These bacterial forms lack virulence factors for intracellular survival and host cell damage, suggesting they are non-pathogenic.
Area of Science:
- Cell Biology
- Microbiology
- Immunology
Background:
- Chlamydia psittaci is an obligate intracellular bacterium.
- Reticulate bodies (RB) are the replicative form of Chlamydia.
- Understanding Chlamydia RB-macrophage interactions is crucial for pathogenesis research.
Purpose of the Study:
- To investigate the interaction between noninfectious Chlamydia psittaci reticulate bodies and mouse peritoneal macrophages.
- To determine if reticulate bodies can survive and replicate within macrophages.
- To assess the cytotoxic effects of reticulate bodies on macrophages.
Main Methods:
- Primary mouse peritoneal macrophages were cultured in monolayers.
- Noninfectious Chlamydia psittaci reticulate bodies were added to macrophage cultures.
- Phagocytosis and intracellular destruction were assessed by measuring radioisotopic counts.
- Cytotoxicity was evaluated by measuring lactic dehydrogenase release.
Main Results:
- Reticulate bodies were readily phagocytized by macrophages.
- A significant decrease (60-70%) in precipitable radioisotopic counts indicated rapid intracellular destruction of RBs within 10 hours.
- Intracellular destruction was independent of the multiplicity of infection.
- High multiplicities of RBs did not induce immediate macrophage cytotoxicity.
Conclusions:
- Noninfectious Chlamydia psittaci reticulate bodies are rapidly destroyed after phagocytosis by macrophages.
- These bacterial forms lack the necessary virulence factors for intracellular survival and host cell damage.
- The RB form of Chlamydia psittaci does not appear to initiate or maintain intracellular survival or cause immediate host cell damage.
