Macrophage activation and resistance to pulmonary tuberculosis.

Mice were vaccinated with 300 micrograms of BCG cell walls (BCG-CW) in oil-in-water emulsion intravenously or with a high or low dose of living BCG by inhalation (BCG-HD or BCG-LD, respectively). The consequences of vaccination were evaluated in terms of the growth of BCG in the lungs and spleen, lung and spleen weight, resistance to intravenous and airborne challenge with Listeria monocytogenes, airborne challenge with virulent Mycobacterium tuberculosis H37Rv, and transfer of adoptive immunity. BCG-CW and BCG-HD mice developed increased lung weight, which was associated with transiet, low-level resistance to airborne L. monocytogenes and initial resistance to airborne H37Rv. Only BCG-CW mice developed splenomegaly, which was accompanied by high resistance to intravenous challenge with L. monocytogenes. The initial resistance of BCG-CW mice to H37Rv was not sustained, whereas that of BCG-HD mice persisted. There was no initial resistance to H37Rv in BCG-LD mice, but immunity was generated later. Overall, BCG-HD mice were most resistant to H37Rv, and BCG-CW and BCG-LD mice were less but equally resistant.