Surfactant protein A enhances alveolar macrophage phagocytosis of a live, mucoid strain of P. aeruginosa

protein A enhances alveolar macrophage phagocytosis of a live, mucoid strain of P. aeruginosa. Am. J. Physiol. 277 (Lung Cell. Mol. Physiol. 21): L777–L786, 1999.—In this study, we investigate the interaction between surfactant protein A (SP-A) and a live, mucoid strain of Pseudomonas aeruginosa and identify a mechanism of clearance of this organism by alveolar macrophages. 125I-labeled SP-A bound live, but not heat-killed, P. aeruginosa organisms in a concentration-dependent manner. Unlabeled SP-A bound live bacteria, protein isolated from whole organisms, and specific proteins of the P. aeruginosa outer membrane. The binding of SP-A to P. aeruginosa and outer membrane components was inhibited by either EDTA or mannose. Phagocytosis assays with fluores-cent microscopy demonstrated that the percentage of macro-phages with internalized FITC-labeled P. aeruginosa wa