Modulation of Rat Bronchoalveolar Lavage Cell Function by the Intratracheal Delivery of Interferon-γ

To determine if there is a rationale for compartmentalized immunostimulation, we have carried out a series of experiments to evaluate whether intratracheal delivery of interferon-γ (rRatIFN-γ) can activate rat bronchoalveolar lavage cells (BAL) for in vitro expression of tumoricidal activity against xenogeneic P815 tumor cells and enhanced in vitro microbicidal activity against the intracellular protozoan Toxoplasma gondii. Treatment of rat alveolar macrophages in vitro activates them for both of these activities as well as enhanced production of Superoxide anion. We found that a single intratracheal dose of 5,000-10,000 units of rRatIFN-γ activated rat BAL for both microbicidal and tumoricidal activity. To determine the duration of activation, microbicidal activity was determined 1, 2, 3, 5, and 7 days after a single intratracheal dose of 5,000 units of IFN. Enhanced microbicidal activity was maintained through day 3 but returned to control levels by day 5. Alveolar macrophages always accounted for the m...