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The effect of immunosuppression on resistance to Rhodococcus equi in mice
P M Bowles1, J B Woolcock, M D Mutimer
1Department of Veterinary Pathology & Public Health, University of Queensland, St. Lucia, Australia.
Veterinary Immunology and Immunopathology
|November 15, 1989
Summary
Cyclophosphamide and cortisone acetate treatments in mice infected with Rhodococcus equi led to lesion development similar to foals. This highlights the role of cell-mediated immunity and macrophages in fighting this bacterial pathogen.
Area of Science:
- Immunology
- Microbiology
- Veterinary Pathology
Background:
- Rhodococcus equi is a significant pathogen in horses, causing disease.
- Experimental models are crucial for understanding host-pathogen interactions and immune responses.
- The role of specific immunosuppressive agents in modulating Rhodococcus equi infection is not fully elucidated.
Purpose of the Study:
- To investigate the impact of various immunosuppressive agents on the development of Rhodococcus equi-induced lesions in mice.
- To assess the influence of immunosuppression on bacterial clearance and host cellular responses.
- To elucidate the role of cell-mediated immunity and macrophage function in resistance to Rhodococcus equi.
Main Methods:
- Experimental infection of mice with Rhodococcus equi via intravenous or intranasal routes.
- Administration of various immunosuppressive agents, including cyclophosphamide, cortisone acetate, carbon, carrageenan, silica, and dextran sulfate.
- Measurement of bacterial growth, histological examination of lesions, and assessment of cellular infiltration at infective foci.
Main Results:
- Cyclophosphamide treatment induced lesions similar to those observed in natural foal infections.
- Cortisone acetate impaired bacterial clearance and mononuclear cell accumulation.
- Agents targeting macrophage function generally did not affect resistance, except for dextran sulfate which impaired clearance and elimination upon rechallenge.
Conclusions:
- Cell-mediated immunity is critical for host resistance against Rhodococcus equi.
- Activated macrophages play a significant role in acquired immunity to this pathogen.
- Specific immunosuppressive agents can exacerbate Rhodococcus equi pathogenesis, providing insights into disease mechanisms.