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Cell size of alveolar macrophages: an interspecies comparison
F Krombach1, S Münzing, A M Allmeling
1Institute for Surgical Research, University of Munich, Germany. krombach@icf.med.uni-muenchen.de
Abstract:
Alveolar macrophages (AM) play a critical role in the removal of inhaled particles or fibers from the lung. Species differences in AM size may affect the number and size range of particles/fibers that can be actually phagocytized and cleared by AM. The purpose of this study was to compare the cell size of rat, hamster, monkey, and human AM by selective flow cytometric analysis of cell volume. Resident AM from CD rats, Syrian golden hamsters, cynomolgus monkeys, and nonsmoking, healthy human volunteers were harvested by standard bronchoalveolar lavage procedures. Morphometric analysis of AM was performed using a flow cytometer that generates volume signals based on the Coulter-type measurement of electrical resistance. We found that hamster and rat AM had diameters of 13.6 +/- 0.4 microns (n = 8) and 13.1 +/- 0.2 microns (n = 12), respectively. Comparatively, the AM from monkeys (15.3 +/- 0.5 microns, n = 7) and human volunteers (21.2 +/- 0.3 microns, n = 10) were larger than those from rats and hamsters. The AM from humans were significantly larger (p < 0.05) than those from all other species studied, corresponding to a 4-fold larger cell volume of human AM (4990 +/- 174 microns 3) compared to hamster (1328 +/- 123 microns 3) and rat (1166 +/- 42 microns 3) AM. In summary, we have found marked species differences in the cell size of AM. We suggest that the number and size range of particles/fibers that can be phagocytized and cleared by AM may differ among species due to inherent or acquired species differences in AM cell size.
Insights
Species differences in alveolar macrophage (AM) size impact particle clearance. Human AM are significantly larger than those in rats, hamsters, and monkeys, affecting phagocytic capacity.
Area of Science:
- Pulmonary immunology
- Cell biology
- Comparative physiology
Background:
- Alveolar macrophages (AM) are crucial for lung defense against inhaled foreign materials.
- Variations in AM size across species may influence their capacity to phagocytize and clear particles and fibers.
Purpose of the Study:
- To investigate and compare the cell size of alveolar macrophages (AM) across different species: rats, hamsters, monkeys, and humans.
- To determine if species-specific AM size differences exist and their potential implications for lung clearance mechanisms.
Main Methods:
- Resident AM were collected from rats, Syrian golden hamsters, cynomolgus monkeys, and human volunteers using bronchoalveolar lavage.
- Cell volume was analyzed using flow cytometry with Coulter-type electrical resistance measurements for morphometric analysis.
Main Results:
- Hamster and rat AM exhibited similar diameters (approx. 13.1-13.6 microns).
- Monkey AM were larger (approx. 15.3 microns), while human AM were significantly larger (approx. 21.2 microns).
- Human AM possessed a 4-fold greater cell volume compared to rat and hamster AM.
Conclusions:
- Marked species-specific differences in AM cell size were observed.
- These size variations suggest that the phagocytic and clearance capabilities of AM for particles and fibers may differ significantly across species.