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Published on: October 25, 2019
Characterization of host cell death induced by Chlamydia trachomatis
Songmin Ying1, Silke F Fischer, Matthew Pettengill
1Institute for Medical Microbiology, Immunology and Hygiene, Technical University Munich, Germany.
Infection and Immunity
|August 31, 2006
Summary
Chlamydia trachomatis infection induces host cell death with some apoptotic features but without activating the classical apoptotic pathway. Dying cells are cleared by phagocytes, potentially influencing the immune response.
Area of Science:
- Microbiology
- Cell Biology
- Immunology
Background:
- Chlamydia are intracellular bacteria known to manipulate host cell apoptosis.
- Previous studies show conflicting results regarding Chlamydia's role in inducing or inhibiting apoptosis.
- Defining the precise mechanism of Chlamydia-induced cell death is crucial for understanding infection dynamics.
Purpose of the Study:
- To precisely define the type of cell death induced by Chlamydia trachomatis infection.
- To investigate the role of mitochondrial apoptosis effectors (Bax and Bak) in this process.
- To explore the implications of Chlamydia-induced cell death in the host immune response.
Main Methods:
- Utilized established apoptosis assays, including TUNEL staining and assessment of nuclear morphology.
- Examined nuclear changes in fibroblasts deficient in Bax and Bak, key mitochondrial apoptosis regulators.
- Observed the uptake of dying infected cells by professional phagocytes.
Main Results:
- Infected cells exhibited morphological signs of apoptosis, such as nuclear condensation and fragmentation, and positive TUNEL staining.
- Genomic DNA fragmentation was observed but presented atypically.
- No evidence of effector caspase activation was found.
- Cell death was significantly, though not completely, dependent on Bak, and partially on Bax.
- Dying Chlamydia-infected cells were efficiently phagocytosed.
Conclusions:
- Chlamydia trachomatis infection does induce host cell death.
- While exhibiting some apoptotic features, this cell death pathway is not mediated by classical effector caspase activation.
- The involvement of Bak suggests a complex interplay with mitochondrial apoptosis pathways.
- Phagocytosis of dying cells indicates a potential role in modulating the host immune response.
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