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Lymphokine-mediated microbistatic mechanisms restrict Chlamydia psittaci growth in macrophages
Abstract:
The obligate intracellular procaryote Chlamydia psittaci replicated in cultures of macrophages taken from the peritoneal cavities of unstimulated or thioglycollate-elicited A/J mice. When treated with supernatant fluids (lymphokines) from C. psittaci-immune mice spleen cells that were stimulated for 24 hr in vitro by the mitogen concanavalin A, resident macrophages supplemented with heart infusion broth (8 mg/ml) and elicited macrophages markedly suppressed intracellular chlamydial development. Uptake of the parasites was unaffected by LK-activated macrophages. The LK-induced inhibition was a static rather than a cidal effect. Chlamydial replication was detected 24 to 41 hr after removal of LK and infection with C. psittaci. Evidence that intermediates of oxygen metabolism did not contribute to the microbistatic process in either resident or elicited macrophages was provided by the inability of exogenous catalase, deprivation of glucose, or pretreatment with phorbol myristate acetate (PMA) to reverse LK-induced inhibition of parasite replication.
Insights
Lymphokines from immune mouse spleen cells suppressed Chlamydia psittaci growth in macrophages. This immune response inhibited parasite development without killing them, offering insights into controlling chlamydial infections.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Chlamydia psittaci is an obligate intracellular bacterium.
- Macrophages play a crucial role in the host immune response against intracellular pathogens.
Purpose of the Study:
- To investigate the effect of lymphokines (LK) from immune mouse spleen cells on Chlamydia psittaci replication within macrophages.
- To determine if LK-induced inhibition of chlamydial development is static or cidal and to explore the mechanisms involved.
Main Methods:
- Culturing macrophages from unstimulated and elicited A/J mice.
- Treating macrophages with lymphokines derived from concanavalin A-stimulated immune spleen cells.
- Assessing Chlamydia psittaci replication and uptake in treated and untreated macrophages.
- Investigating the role of oxygen metabolism intermediates by using catalase, glucose deprivation, and phorbol myristate acetate (PMA).
Main Results:
- Lymphokines markedly suppressed intracellular Chlamydia psittaci development in both resident and elicited macrophages.
- Parasite uptake remained unaffected by LK-activated macrophages.
- The inhibition was determined to be a static, not cidal, effect, with replication resuming after LK removal.
- Oxygen metabolism intermediates were not found to contribute to the microbistatic process.
Conclusions:
- Immune mouse spleen cell-derived lymphokines can effectively suppress Chlamydia psittaci replication within macrophages.
- The mechanism of suppression is primarily static, halting parasite development rather than eliminating it.
- This study highlights a potential immunomodulatory strategy for controlling chlamydial infections.