Surfactant protein A enhances alveolar macrophage phagocytosis of a live, mucoid strain of P. aeruginosa.
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. (125)I-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 fluorescent microscopy demonstrated that the percentage of macrophages with internalized FITC-labeled P. aeruginosa was increased 1.8-fold (19 vs. 35%) by pretreating the live bacteria with SP-A. This finding was confirmed by direct visualization of ingested bacteria by electron microscopy. Adhering macrophages to SP-A-coated surfaces attenuated the increased uptake of P. aeruginosa pretreated with SP-A, suggesting that SP-A acts as an opsonin to stimulate macrophage phagocytosis of this strain of P. aeruginosa.
Mariencheck
W I
WI
Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.
Savov
J
J
Dong
Q
Q
Tino
M J
MJ
Wright
J R
JR
D000818:Animals; D002448:Cell Adhesion; D002462:Cell Membrane / Q000378:metabolism; D016676:Macrophages, Alveolar / Q000187:drug effects* / Q000502:physiology* / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D010587:Phagocytosis / Q000187:drug effects*; D011510:Proteolipids / Q000378:metabolism / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000378:metabolism / Q000502:physiology*; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats
D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants