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Published on: April 12, 2019
Effect of intravenous silica on the course of Nocardia asteroides pneumonia
1Infectious Disease Section, Veterans Administration Medical Center, Minneapolis, Minnesota 55417.
Abstract:
Silica, a known toxin of mononuclear phagocytes, was administered intravenously to mice during Nocardia asteroides pneumonia. Mice that received silica had a sevenfold decrease in the number of peripheral blood monocytes and developed more severe N. asteroides pneumonia than control mice. Lung histology in mice that received silica resembled that of mice with impaired cell-mediated immunity. These results are most consistent with the explanation that silica injures blood monocytes and impairs their contributions to pulmonary host defense.
Insights
Silica exposure significantly reduced monocytes in mice with Nocardia asteroides pneumonia, leading to more severe lung disease. This suggests silica impairs critical immune cell functions in pulmonary infections.
Area of Science:
- Immunology
- Infectious Diseases
- Toxicology
Background:
- Mononuclear phagocytes are crucial for host defense during bacterial pneumonia.
- Silica is a known toxin affecting phagocytic cells.
- Nocardia asteroides pneumonia serves as a model for bacterial lung infection.
Purpose of the Study:
- To investigate the impact of silica administration on the course of Nocardia asteroides pneumonia in mice.
- To determine if silica affects monocyte populations and their function in pulmonary immunity.
Main Methods:
- Intravenous administration of silica to mice during experimental Nocardia asteroides pneumonia.
- Quantification of peripheral blood monocyte counts.
- Histological examination of lung tissue to assess inflammatory responses and tissue damage.
Main Results:
- Mice receiving silica showed a sevenfold decrease in peripheral blood monocytes compared to controls.
- Silica-treated mice developed significantly more severe Nocardia asteroides pneumonia.
- Lung histology in silica-exposed mice indicated impaired cell-mediated immunity.
Conclusions:
- Silica injures blood monocytes, compromising their role in pulmonary host defense.
- Impaired monocyte function due to silica exacerbates bacterial pneumonia severity.
- These findings highlight silica's detrimental effect on immune responses to lung infections.
