Effects of hydrocortisone acetate on pulmonary alveolar macrophage colony-forming cells.

We investigated the effect of prolonged monocytopenia induced by daily injections of hydrocortisone acetate on the number of alveolar cells and alveolar macrophage colony-forming cells (AL-CFC) in mice. We did not observe an appreciable reduction in the number of either alveolar macrophages of AL-CFC under this experimental condition, which markedly inhibited the blood monocyte concentration over 10 days. These results suggest the existence of a mechanism by which the number of alveolar macrophages, including AL-CFC, can be maintained without a continuous migration of blood monocytes into alveolar spaces.