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Subpopulations of human lung alveolar macrophages: ultrastructural features
B Nakstad1, T Lyberg, F Skjörten
1Department of Pathology, Ullevaal Hospital, University of Oslo, Norway.
Abstract:
Lung alveolar macrophages (LAM), obtained by bronchoalveolar lavage of healthy donors, were separated into four subfractions on discontinuous gradients of Percoll and subjected to light microscopic, transmission (TEM) and scanning electron microscopic (SEM) studies. Alveolar macrophage morphometric analysis was performed on cytocentrifuged preparations. TEM of subpopulations revealed considerable morphologic heterogeneity. By SEM, cells of the most dense (D) subfraction were small, round, and, typically, the surface was highly ruffled with small membrane pseudopods. Cells of the least dense subfraction (A) showed a low degree of membrane folding or filopodia and were often totally disorganized. In smokers, macrophages of fraction A had a greater area and perimeter compared with non-smokers, whereas the inverse relationship was observed for C and D cells. Also, the number of electron-dense inclusions and the level of acid phosphatase were higher in smokers than in non-smokers. Coupled with functional heterogeneity the morphologic differences described in this paper suggest that density-separated subpopulations of LAM may represent different stages of differentiation or maturation.
Insights
Lung alveolar macrophages (LAM) exhibit distinct morphologies across density subfractions, suggesting different differentiation stages. Smokers show altered macrophage characteristics compared to non-smokers.
Area of Science:
- Cell Biology
- Immunology
- Pulmonary Medicine
Background:
- Lung alveolar macrophages (LAM) are crucial immune cells in the lungs.
- Previous studies suggest functional heterogeneity within LAM populations.
Purpose of the Study:
- To investigate the morphological heterogeneity of LAM subpopulations.
- To compare LAM morphology between smokers and non-smokers.
Main Methods:
- Separation of LAM into four subfractions using Percoll density gradients.
- Morphological analysis using light microscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM).
- Morphometric analysis of cytocentrifuged preparations.
Main Results:
- Significant morphological heterogeneity was observed among LAM subpopulations via TEM and SEM.
- Dense subfractions (D) showed small, round cells with ruffled surfaces; less dense fractions (A) were disorganized.
- Smokers exhibited larger area and perimeter in fraction A LAM, with higher electron-dense inclusions and acid phosphatase levels compared to non-smokers.
Conclusions:
- Density-separated LAM subpopulations display distinct morphological features.
- These morphological differences suggest varying stages of differentiation or maturation in LAM.
- Smoking significantly impacts LAM morphology and cellular content.