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[Foamy alveolar macrophages in various lung diseases, and their origin in rabbit lungs]
1Second Department of Internal Medicine, Hirosaki University School of Medicine, Aomori-Prefecture, Japan.
Abstract:
The present studies were done to clarify the significance of foamy alveolar macrophages (FAM) in lung diseases, and the mechanism of the production of macrophages in rabbit lungs. Human subjects consisted of 18 normal volunteers (NV) and 47 patients with lung disorders: chronic bronchitis (CB), 7 cases; pulmonary fibrosis (PF), 8 cases; old pulmonary tuberculosis (OPT), 7 cases; lung cancer (LC), 20 cases; and bronchiectasis (BE), 5 cases. In each case, over 30 macrophages in the BALF were observed by transmission electron microscopy. There were no significant differences in the percentage of FAm in the BALF among NV, CB, and PF. Furthermore, OPT and LC were not significantly different. Many more FAM were seen in OPT and LC than in NV, CB, and PF (p < 0.005). The percentage of FAM obtained from BE was much higher than that from OPT and LC (p < 0.005). These results suggest that the grade of foamy change in macrophages differs among lung diseases. Three groups of rabbits were studied. Group I rabbits (n = 6) were control, Group II rabbits (n = 6) underwent bronchial clamping, and Group III rabbits (n = 6) underwent complete replacement of blood with saline. The number of macrophages and type II cells was much greater in Group II rabbits than in Group I rabbits. In Group III rabbits, the number of macrophages was lower than in Group I rabbits. In Group III rabbits, vacuole-like structures were seen in the cytoplasma of type II cells, but not from in macrophages. These findings suggest that anoxia and blood flow are important for the appearance of macrophages in alveolar space. Group III rabbits had few alveolar macrophages. Therefore, alveolar macrophages may be derived from monocytes in blood.
Insights
Foamy alveolar macrophages (FAM) are more prevalent in severe lung diseases like old pulmonary tuberculosis and lung cancer. Rabbit studies suggest anoxia and blood flow influence macrophage production, potentially from blood monocytes.
Area of Science:
- Pulmonary pathology
- Cell biology
- Immunology
Context:
- Foamy alveolar macrophages (FAM) are implicated in various lung diseases.
- Understanding FAM's role and origin is crucial for diagnosing and treating lung disorders.
- Previous research has not fully elucidated the mechanisms behind FAM accumulation or their cellular origins.
Purpose:
- To investigate the significance of foamy alveolar macrophages (FAM) in different human lung diseases.
- To explore the mechanisms of macrophage production in rabbit lungs, focusing on the role of anoxia and blood flow.
Summary:
- Human studies revealed significantly higher percentages of FAM in patients with old pulmonary tuberculosis (OPT), lung cancer (LC), and bronchiectasis (BE) compared to normal volunteers (NV), chronic bronchitis (CB), and pulmonary fibrosis (PF).
- Bronchiectasis showed the highest FAM percentage, exceeding even OPT and LC.
- Rabbit models indicated that bronchial clamping (Group II) increased macrophage and type II cell counts, while blood replacement with saline (Group III) decreased macrophage numbers and showed vacuole-like structures in type II cells, suggesting anoxia and blood flow are key factors.
- The scarcity of alveolar macrophages in Group III rabbits suggests a potential origin from circulating monocytes.
Impact:
- These findings highlight the differential prevalence of FAM across various lung pathologies, suggesting their potential as diagnostic or prognostic biomarkers.
- The study provides insights into the dynamic regulation of alveolar macrophages, influenced by oxygen levels and vascular supply.
- The proposed monocyte origin of alveolar macrophages warrants further investigation for therapeutic strategies targeting lung inflammation and repair.