Interspecies differences in the phagocytic activity of pulmonary macrophages subjected to acidic challenge

Examining interspecies differences in response to ambient pollutants is an essential component of risk assessment. The potential hazard to public health from the inhalation of acid sulfate aerosols is of current concern. A significant biological target is the pulmonary macrophage, which provides a primary defense of the respiratory region of the lungs. One essential function of these cells is phagocytosis of particles. This study assessed the effects of acidic environments on the phagocytic activity of pulmonary macrophages obtained by lavage from humans and three species of laboratory animals commonly used in acid aerosol toxicology studies, namely, rats, rabbits, and guinea pigs. Cells were incubated with polystyrene latex particles in media acidified by addition of sulfuric acid. The percentage of cells which were phagocytic, as well as the relative number of particles ingested by these cells, was found to decrease with increasing acidity for all species. The ranking of response in order of decreasing sensitivity to acidic challenge was as follows: guinea pig > rat > rabbit > human.