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Cellular immunity of mice infected with Listeria monocytogenes in diffusion chambers
Abstract:
The importance of bringing live bacteria into intimate contact with macrophages as a prerequisite for establishing cellular immunity was investigated. The bacterium Listeria monocytogenes was shown to replicate and survive in diffusion chambers implanted in the peritoneal cavities of mice. Humoral substances accruing from host responses to diffusing soluble antigens of the microorganism were unable to inactivate the bacteria. The resistance of mice immunized by subcutaneous inoculation of the live organism always exceeded the resistance of mice with Listeria diffusion chamber implants. Animals with sham diffusion chambers were more resistant to a challenge by L. monocytogenes than were normal mice. Host resistance was not significantly different between Listeria diffusion chamber implant groups and sham diffusion chamber implant groups. The results suggested that direct involvement of macrophages with the parasite is necessary to achieve cellular immunity.
Insights
Direct contact between macrophages and live bacteria like Listeria monocytogenes is crucial for developing cellular immunity. Soluble immune factors alone were insufficient to control bacterial growth and confer resistance.
Area of Science:
- Immunology
- Microbiology
- Cellular Biology
Background:
- Cellular immunity is vital for host defense against intracellular pathogens.
- The role of direct macrophage-bacterial interaction in initiating immunity requires clarification.
Purpose of the Study:
- To investigate the necessity of direct contact between live bacteria and macrophages for establishing cellular immunity.
- To determine if humoral immune responses alone can control Listeria monocytogenes infection in vivo.
Main Methods:
- Listeria monocytogenes (L. monocytogenes) survival and replication were assessed in diffusion chambers implanted in mice.
- Comparison of host resistance in mice with L. monocytogenes diffusion chambers, sham chambers, and subcutaneous immunization.
- Evaluation of the efficacy of humoral substances against L. monocytogenes in the peritoneal cavity.
Main Results:
- L. monocytogenes replicated and survived within peritoneal diffusion chambers, indicating limited control by diffusing humoral factors.
- Mice immunized subcutaneously with live L. monocytogenes exhibited greater resistance than those with diffusion chamber implants.
- Animals with sham diffusion chambers showed enhanced resistance compared to normal mice, but no significant difference was observed between Listeria and sham chamber groups.
Conclusions:
- Direct interaction between macrophages and live Listeria monocytogenes is essential for inducing effective cellular immunity.
- Humoral immune responses alone are insufficient to eliminate intracellular bacterial infections.
- Macrophage engagement with the pathogen is a prerequisite for protective cellular immunity.