Superoxide production in pulmonary alveolar macrophages and killing of BCG by the superoxide-generating system with or without catalase.

Abstract

The superoxide production of BCG-infected and noninfected alveolar macrophages was measured by superoxide dismutase-inhibitable nitro blue tetrazolium reduction. The cells were incubated with or without cell-free bronchial lavage fluid (pulmonary washings). When control alveolar macrophages were infected by BCG, superoxide production was decreased markedly, probably due to bacterial cytotoxic factors. In contrast, the production of superoxide in alveolar macrophages exposed to pulmonary washings was increased and not appreciably influenced by BCG infection. Superoxide production by alveolar macrophages was dependent on time and on the protein concentration in the pulmonary washings. In controls, it was inversely proportional to the infecting dose of BCG. We observed previously that alveolar macrophages activated by pulmonary washings inhibited intracellular growth of BCG. We now present evidence that enhanced production of superoxide contributes to such inhibition, especially in the presence of catalase at acid pH. These findings are pertinent to the defense of inflamed lungs, where serum and serum immunoglobulin G transuded from blood into alveolar spaces probably induce such activation on alveolar macrophages.