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Mycoplasma pulmonis arthritis in congenitally athymic (nude) mice. Histopathological features
Abstract:
Histopathological examinations were performed on arthritis joints and other organs of strain BALB/cA nu/nu and nu/+ mice intravenously injected with Mycoplasma pulmonis strain m53. In both groups of mice suffering from polyarthritis, acute inflammatory lesions with infiltration of polymorphonuclear leukocytes in the synovia and periarticular tissues were observed one to two weeks after injection. In nu/nu mice, the acute inflammation appeared repeatedly up to 20 weeks after inoculation, when the experiment was terminated, and furthermore, extensive synovial and periarticular necrosis were characteristically present after the 4th week. Only a small number of lymphocytes and plasma cells were in the lesions. In nu/+ mice, after the early acute inflammation of arthritis, relapses of the infiltration of polymorphonuclear leukocytes were also observed in some mice in and after the 10th week. In addition, infiltration of lymphocytes and plasma cells were substantial after the 15th week. Focal necrosis was sometimes found in the liver of nu/nu mice. Perivascular infiltration of small lymphocytes and plasma cells was found in the lungs, liver and kidney of nu/+ mice in and after the 15th week. Repair mechanisms of injured articular tissues in nu/nu mice were histopathologically poor, while those in nu/+ mice seemed to be progressive and quite similar to those reported by many investigators for mice with the thymus intact. The histopathological differences are discussed in respect to the thymus-dependent immune responses.
Insights
Mycoplasma pulmonis infection causes polyarthritis in mice. Athymic (nu/nu) mice show severe, recurring inflammation and necrosis, while thymus-bearing (nu/+) mice exhibit a more typical immune response with later lymphocyte infiltration and better tissue repair.
Area of Science:
- Immunology
- Pathology
- Microbiology
Background:
- Mycoplasma pulmonis is a pathogen that can cause respiratory and systemic infections.
- The role of the thymus in immune responses to Mycoplasma pulmonis-induced arthritis is not fully understood.
Purpose of the Study:
- To investigate the histopathological differences in arthritis and organ involvement between athymic (nu/nu) and thymus-bearing (nu/+) mice infected with Mycoplasma pulmonis.
- To elucidate the role of thymus-dependent immune responses in the pathogenesis and resolution of Mycoplasma pulmonis-induced polyarthritis.
Main Methods:
- BALB/cA nu/nu and nu/+ mice were intravenously injected with Mycoplasma pulmonis strain m53.
- Histopathological examinations of joints and other organs were performed at various time points post-infection.
Main Results:
- Both mouse groups developed acute inflammatory lesions with polymorphonuclear leukocytes infiltration.
- Athymic mice exhibited repeated acute inflammation, extensive synovial/periarticular necrosis, and poor tissue repair.
- Thymus-bearing mice showed relapsing inflammation, later infiltration of lymphocytes/plasma cells, and progressive repair mechanisms.
Conclusions:
- The thymus plays a critical role in mediating effective immune responses against Mycoplasma pulmonis-induced polyarthritis.
- Athymic mice are susceptible to severe, chronic inflammation and tissue damage due to a lack of thymus-dependent immunity.
- Histopathological findings highlight significant differences in disease progression and resolution based on thymus presence.