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Granulomatous lesions in the lung induced by inhalation of mold spores
1Laboratory of Germfree Life, Nagoya University School of Medicine, Japan.
Abstract:
The health hazards associated with grain dust exposure have been recognized as a cause of lung diseases. In the present study, we used germ-free rats exposed to Aspergillus versicolor to elucidate the mechanism for the lung damage induced by grain dust exposure. One month after exposure to the mold, remarkable proliferation of bronchus-associated lymphoid tissues with germinal centres was induced by aspiration of mold spores. After 1 month, alveolar macrophages increased, becoming foamy macrophages by ingestion and digestion of mold spores. They expressed interleukin (IL)-1, Ia antigens and intercellular adhesion molecule-1 intensely and occasionally bound lymphocytes. Numerous lymphocytes infiltrated the granulomatous lesions which consisted of accumulated foamy macrophages and some T lymphocytes which carried IL-2 receptor. Granulomatous lesions were identified in the entire lung, especially around bronchioles. They extended from alveolar ducts to alveolar spaces for 6 months after exposure to the mold. The macrophage appears to be a key effector cell in granulomatous reactions to inhaled molds.
Insights
Grain dust exposure causes lung disease. In germ-free rats, mold spore inhalation led to lung inflammation and granuloma formation, with macrophages playing a key role in the immune response.
Area of Science:
- Immunology
- Pulmonology
- Environmental Health
Background:
- Grain dust exposure is linked to lung diseases.
- The specific mechanisms of lung damage from grain dust remain unclear.
- Aspergillus versicolor is a common mold found in grain dust.
Purpose of the Study:
- To elucidate the mechanism of lung damage induced by grain dust exposure.
- To investigate the role of Aspergillus versicolor in lung inflammation.
- To identify key cellular players in the granulomatous response to inhaled mold spores.
Main Methods:
- Germ-free rats were exposed to Aspergillus versicolor.
- Lung tissues were analyzed for inflammatory markers and cellular infiltration.
- Immunohistochemistry was used to identify cell types and their activation states.
Main Results:
- Inhaled mold spores induced proliferation of bronchus-associated lymphoid tissues.
- Alveolar macrophages transformed into foamy macrophages, expressing IL-1, Ia antigens, and ICAM-1.
- Granulomatous lesions, characterized by foamy macrophages and T lymphocytes, formed throughout the lungs and persisted for 6 months.
Conclusions:
- Macrophages are key effector cells in granulomatous reactions to inhaled molds.
- Aspergillus versicolor exposure in germ-free rats mimics lung damage seen in grain dust exposure.
- This study provides insights into the pathogenesis of mold-induced lung disease.