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Electron microscopy of the in vivo internalization of virulent Chlamydia psittaci 6BC strain
Abstract:
The internalization of virulent Chlamydia psittaci 6BC particles by wandering mononuclear phagocytes in the peritoneal cavity of intraperitoneally inoculated mice occurred asynchronously, i.e., fragile reticulate bodies (RB) appeared to be more readily phagocytized than the rigid elementary bodies (EB). Early damage of mononuclear phagocytes occurred after internalization of chlamydiae. This was followed by a decreased uptake of particles, and may explain the relatively long persistence (up to 6 h after inoculation) of free, extracellular, "swollen", and RB-like particles. Internalized particles within phagolysosomes showed varying degrees of disintegration. The subsequent influx of polymorphonuclear phagocytes and monocytes into the inflammed peritoneal cavity may explain the rapid disappearance of chlamydiae and their antigens from the peritoneal fluid. The alteration in ultrastructure of peritoneal cells and chlamydial parasites during the inflammatory process are discussed.
Insights
Chlamydia psittaci 6BC infects mouse peritoneal cells, with reticulate bodies (RB) phagocytized more readily than elementary bodies (EB). Early cell damage and later immune cell influx influence chlamydial persistence and clearance.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Chlamydia psittaci is an obligate intracellular bacterium causing psittacosis.
- Understanding its interaction with host immune cells is crucial for disease pathogenesis.
Purpose of the Study:
- To investigate the early events of Chlamydia psittaci 6BC infection in mouse peritoneal cells.
- To characterize the phagocytosis and intracellular fate of chlamydial particles.
Main Methods:
- Intraperitoneal inoculation of mice with Chlamydia psittaci 6BC.
- Ultrastructural analysis of peritoneal cells and chlamydial particles over time.
Main Results:
- Asynchronous phagocytosis of Chlamydia psittaci 6BC, with reticulate bodies (RB) favored over elementary bodies (EB).
- Early damage to mononuclear phagocytes following internalization.
- Reduced particle uptake and extracellular persistence of altered chlamydial forms.
- Disintegration of internalized particles within phagolysosomes.
- Rapid clearance of chlamydiae and antigens mediated by polymorphonuclear leukocytes and monocytes.
Conclusions:
- The study elucidates the dynamic interaction between Chlamydia psittaci and peritoneal phagocytes.
- Host cell damage and subsequent inflammatory cell recruitment dictate chlamydial fate.
- Ultrastructural changes provide insights into the parasite-host interplay during infection.