In vitro phagocytosis of respirable sized monodisperse particles by rabbit alveolar macrophages

Phagocytosis by alveolar macrophages of particles deposited deep in the lung may play an important role in the ultimate fate of the particles. An in vitro system for studying the phagocytosis of insoluble monodisperse particles by rabbit alveolar macrophages was developed to study the influence of particle size, particle concentration and incubation time on phagocytosis. Monodisperse 169Yb-labeled fused aluminosilicate particles and 239PuO2 particles ranging from 0.35 to 2.2 μm in real diameter (aerodynamic diameter = 0.55 - 3.4 μm) were incubated with alveolar macrophages, the free particles separated from the ingested ones, and the number of phagocytized particles determined. Results indicate that the larger particles are taken up more rapidly and in greater numbers than the smaller ones. In addition, greater numbers of the more dense and rapidly settling 239PuO2 particles are taken up than fused aluminosilicate particles of the same real diameter. In vitro studies of the handling of respirable particles by alveolar macrophages may aid in determining the relative importance of phagocytosis in the removal of particles from the deep lung