Impaired Function of Polymorphonuclear Leukocytes Exuded into Bronchoalveolar Spaces Infected with Pseudomonas aeruginosa in Steroid-treated Rabbits

Abstract

Steroid-treated and untreated rabbits were infected transbronchially with Pseudomonas aeruginosa. The polymorphonuclear leukocytes (PMN) exuded into the bronchoalveolar spaces were obtained by lavage 18 hr later, and superoxide (O⁻₂) production and chemotactic activity were studied. In the steroid-treated group, there was a heightened susceptibility to the infection, as compared to findings in the untreated group. The lung exudate PMN in the steroid-treated group showed a significant decrease (p < 0.05) in O⁻₂ production, and somewhat depressed chemotactic activity. In the untreated group, both O⁻₂ production (p < 0.01) and chemotactic activity (p < 0.001) of lung exudate PMN doubled, compared with findings in blood PMN. There was, however, no significant difference between lung exudate PMN and blood PMN in the steroid-treated group. Impaired PMN function in the steroid-treated group was also observed in case of casein-induced lung exudate PMN. These results suggest that the antibacterial function of PMN exuded in the infected lung may be impaired in steroid-treated hosts, hence an enhanced susceptibility to lung infection.