Defective lung macrophages in pulmonary alveolar proteinosis
Abstract:
Lung macrophages obtained by segmental lavage from three patients with pulmonary alveolar proteinosis were studied in vitro. The macrophages exhibited morphologic abnormalities including excessive lipid accumulation and giant secondary lysosome formation. These cells survived poorly in tissue culture, showed impaired chemotactic activity, and had decreased adhesiveness to glass. They phagocytized normally but had substantially decreased capacity to kill ingested Candida pseudotropicalis. Evidence was obtained that the macrophage defect was acquired and probably related to ingestion of the proteinaceous alveolar fluid. Peripheral blood monocyte function was normal in one patient and morphologic abnormalities were produced in normal monocyte-derived macrophages cultured with proteinaceous lavage material. These studies suggest that the lung macrophage in alveolar proteinosis is a defective cell as a consequence of an abnormal pulmonary environment.
Insights
Pulmonary alveolar proteinosis causes lung macrophages to accumulate lipids and form abnormal lysosomes. These defective macrophages have impaired survival and function, suggesting an abnormal lung environment causes the defect.
Area of Science:
- Pulmonary immunology
- Cell biology
Background:
- Pulmonary alveolar proteinosis (PAP) is a rare lung disease characterized by the accumulation of surfactant-like material in the alveoli.
- The role of alveolar macrophages in the pathogenesis of PAP is not fully understood.
Observation:
- Lung macrophages from PAP patients showed excessive lipid accumulation and giant lysosome formation.
- These macrophages exhibited poor survival in culture, reduced chemotaxis, and decreased adhesion.
- Phagocytosis was normal, but the ability to kill ingested Candida pseudotropicalis was significantly impaired.
Findings:
- The observed macrophage defects appear to be acquired, likely due to the ingestion of proteinaceous alveolar fluid.
- Normal monocytes from a patient showed normal function, and normal macrophages exposed to PAP lavage material developed similar abnormalities.
- These findings indicate that the abnormal pulmonary environment in PAP directly impairs lung macrophage function.
Implications:
- Lung macrophages in PAP are functionally defective due to the disease's pathological milieu.
- Therapeutic strategies targeting the alveolar environment or enhancing macrophage function could be beneficial for PAP treatment.
- Further research into macrophage-environment interactions in PAP may reveal novel therapeutic targets.
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