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Pulmonary sarcoidosis: could mycoplasma-like organisms be a cause?
L A Johnson1, J R Edsall, J H Austin
1Department of Pathology, Columbia-Presbyterian Medical Center, New York, N.Y. 10032, USA.
Abstract:
The etiology of sarcoidosis is unknown but an unusual bacterial agent is possible. Mycoplasma-Like Organisms [MLO] are obligate intracellular cell wall deficient bacteria with a distinctive ultrastructural appearance. MLO are a common cause of various transmissible plant diseases. Despite over 25 years of effort MLO remain uncultivated. Molecular biologic studies indicate MLO are only distantly related to extracellular cultivable mycoplasma. Diagnosis of MLO diseases is based chiefly on detection of the organisms in infected cells by electron microscopy. Recently MLO have been detected by electron microscopy within leucocytes in sterile inflamed aqueous and vitreous humor from patients with idiopathic chronic uveitis including sarcoidosis uveitis. Preliminary molecular biologic studies suggest that human MLO are quite closely related phylogenetically to plant MLO. Inoculation of human uveitis MLO into mouse eyelids produced chronic uveitis and lethal systemic granulomatous disease with MLO within leucocytes and endothelial cells in the disease sites. The MLO induced animal pulmonary disease resembled sarcoidosis. This report describes abnormal intracellular bodies consistent with MLO within leucocytes and endothelial cells adjacent to the granulomas in transbronchial biopsies from 9 corticosteroid untreated sarcoidosis patients versus none in 4 control lungs.
Insights
The study suggests Mycoplasma-Like Organisms (MLO) may cause sarcoidosis. Abnormal MLO-like bodies were found in sarcoidosis patients, and MLO induced similar disease in mice.
Area of Science:
- Microbiology
- Immunology
- Ophthalmology
Background:
- The cause of sarcoidosis remains unknown, with unusual bacterial agents being a possibility.
- Mycoplasma-Like Organisms (MLO) are obligate intracellular, cell-wall-deficient bacteria known to cause plant diseases.
- MLO are difficult to cultivate and are phylogenetically distinct from cultivable mycoplasmas.
Purpose of the Study:
- To investigate the potential role of Mycoplasma-Like Organisms (MLO) in the etiology of sarcoidosis.
- To compare MLO found in human uveitis with plant MLO.
- To assess the pathogenicity of human uveitis MLO in an animal model.
Main Methods:
- Electron microscopy was used to detect MLO in ocular fluids of patients with idiopathic chronic uveitis, including sarcoidosis.
- Molecular biologic studies were performed to determine the phylogenetic relationship between human and plant MLO.
- Human uveitis MLO were inoculated into mouse eyelids to observe disease development.
Main Results:
- MLO were detected in leukocytes within the aqueous and vitreous humor of patients with sarcoidosis uveitis.
- Human MLO showed close phylogenetic relation to plant MLO.
- MLO inoculation in mice induced chronic uveitis, lethal systemic granulomatous disease, and pulmonary pathology resembling sarcoidosis.
- Abnormal intracellular bodies consistent with MLO were found in transbronchial biopsies of untreated sarcoidosis patients.
Conclusions:
- MLO are a potential etiological agent for sarcoidosis.
- The findings support the hypothesis that MLO may be involved in the pathogenesis of sarcoidosis.
- Further research is warranted to confirm the role of MLO in human sarcoidosis.