The pulmonary interstitial cell as immediate precursor of the alveolar macrophage.

The origin of the alveolar macrophage was studied in cultured explants of murine lung. In this system, which is free of circulating monocytes, a new population of alveolar macrophages was identified on the third day of culture; immediately preceding the appearance of these cells, proliferation of pulmonary interstitial cells was observed. A temporal relationship between interstitial cells and alve…