Alveolar macrophage subpopulations' responsiveness to chemotactic stimuli

Recent data suggest that alveolar macrophages are a heterogeneous group of cells with several subpopulations. This study was undertaken to determine if there is heterogeneity among rat alveolar macrophage subpopulations ability to respond to chemotactic stimuli. Alveolar macrophages were harvested by bronchoalveolar lavage and fractionated into density-defined fractions by centrifugation through a continuous isoosmotic gradient of colloidal silica. Unfractionated and density-defined alveolar macrophages were then characterized as to their ability to migrate towards F-Met-Leu-Phen and zymosan-activated serum. Alveolar macrophages of density 1.083-1.097 gm/ml were found to have the greatest migrational movement toward F-Met-Leu-Phen, which was higher than the unfractionated population. In contrast, 2 peaks in alveolar macrophage subpopulations migrational movement towards zymosan-activated serum were noted that were lower than the unfractionated population. These results demonstrated that alveolar macrophages are heterogeneous in their migrational ability towards the chemotactic stimuli F-Met-Leu-Phen and zymosan-activated serum and that there may be a cooperative interaction between the subpopulations that affects macrophage migrational ability.