Interstitial macrophage subpopulations: responsiveness to chemotactic stimuli.

Recent data suggest that interstitial macrophages are a heterogeneous group of cells with several subpopulations. This study was undertaken to determine if there is heterogeneity among rat interstitial macrophage subpopulations ability to respond to chemotactic stimuli. Alveolar macrophages were harvested and separated into density-defined fractions by centrifugation through a continuous iso-osmotic gradient of colloidal silica. Unfractionated and density-defined interstitial macrophages were then characterized as to their ability to migrate towards F-Met-Leu Phen and zymosan activated serum. Interstitial macrophages of density 1.053 and 1.083-1.097 gm/ml were found to have the greatest migrational movement towards F-Met-Leu-Phen which was lower than the unfractionated population. Interstitial macrophage subpopulations migrational movement towards zymosan activated serum exhibited a major peak by macrophages of density 1.053 gm/ml and a minor peak by macrophages of density 1.083-1.097 gm/ml which was lower than the unfractionated population. These results demonstrated that interstitial 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 which affects macrophages migrational ability.