Inhibitory role of alveolar macrophages in colony-stimulating factor production by the lung tissue from bacillus Calmette-Guérin-treated animals.

Production of colony-stimulating factors (CSF) by lung tissue from rats injected by bacillus Calmette-Guerin (BCG) and the role of alveolar macrophages (AM) in this process was studied. Injection of BCG at 10, 100, or 1,000 mg/kg changed the CSF production by the lung in a time-dependent manner. Maximum stimulation was observed at 10 mg/kg and 3 days of interval between BCG injection and animal sacrifice. Longer periods or higher concentrations had no effect or actually depressed CSF production. BCG injection also changed the number of AM in a time- and dose-dependent manner. When AM from BCG-treated animals were lavaged out and the AM-depleted lung tissues were cultured, an increase in CSF production with respect to controls was observed at 10 mg/kg of BCG. On the other hand, in control animals removal of AM had no effect on CSF production by the lung. The results suggest that BCG treatment alters the number of AM and CSF production by the lung. AM, in BCG-injected animals, inhibit CSF production by the lung tissue while in non-injected animals they do not play any role in this process.