Dependence on particle size in the phagocytosis of latex particles by rabbit alveolar macrophages cultured in vitro.

The dependence of the phagocytosis of particulate materials on their size was studied. Rabbit alveolar macrophages (AMs) obtained by lung lavage were cultured in suspensions or monolayers with Latex particles of 1 micron or 2 microns in diameter. After culturing AMs with 10(7)(-5) X 10(9) Latex particles per ml for 15 to 360 minutes, the number of phagocytized particles in each of 100 individual cells was counted by light microscopy. In suspension culture, there was no significant difference in the average number of particles phagocytized per AM between 1 micron and 2 microns particles in the identical conditions as to the particle concentration (particle number/ml) and the incubation time. In monolayer culture, it was difficult to compare the average number of 1 micron particles phagocytized by AM with that of 2 microns ones in the identical condition as to the particle concentration, since the sedimentation velocities at which particles sank to the bottom of culture chamber were different between both particles, resulting in the difference of particle concentration around AMs. The sign of saturation was observed when the average number of phagocytized particles reached approximately 10 particles per AM in either case of suspension culture with 1 micron or 2 microns particles and approximately 45 of 1 micron and 10 of 2 microns particles in monolayer culture.