Surfactant protein D stimulates phagocytosis of Pseudomonas aeruginosa by alveolar macrophages.
Surfactant protein (SP)-D is an oligomeric glycoprotein belonging to the family of collagen-like lectins known as collectins, which have previously been shown to stimulate phagocytosis and other immune cell functions. The hypothesis investigated in this study was that SP-D would stimulate the phagocytosis of an important pulmonary pathogen, Pseudomonas aeruginosa. SP-D, isolated from the lavage fluid of silica-treated rats, significantly enhanced the uptake of three of six strains of P. aeruginosa by rat alveolar macrophages as analyzed by both fluorescence and electron microscopy. SP-D had only minimal effects on phagocytosis of Haemophilus influenzae. SP-D bound to live P. aeruginosa, and binding was inhibited by chelation of calcium and by a competing saccharide, inositol. In vitro killing assays demonstrated that macrophage-mediated killing of one of the mucoid strains of P. aeruginosa was modestly enhanced by SP-D. P. aeruginosa was not measurably aggregated by SP-D either macroscopically or microscopically. Further, SP-D does not appear to act as an activation ligand because adherence of macrophages to SP-D- coated slides did not stimulate the uptake of P. aeruginosa. These findings suggest that SP-D may be important in controlling the pathogenesis of P. aeruginosa in the lung.
Restrepo
C I
CI
Department of Medicine, Durham Veterans Administration Medical Center Research Service, Duke University Medical Center, Durham, North Carolina 27710, USA.
Dong
Q
Q
Savov
J
J
Mariencheck
W I
WI
Wright
J R
JR
D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D006023:Glycoproteins / Q000378:metabolism / Q000494:pharmacology*; D006358:Hot Temperature; D008262:Macrophage Activation / Q000187:drug effects; D016676:Macrophages, Alveolar / Q000187:drug effects* / Q000276:immunology / Q000382:microbiology / Q000648:ultrastructure; D008297:Male; D008320:Maltose / Q000494:pharmacology; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D009895:Opsonin Proteins / Q000494:pharmacology; D010587:Phagocytosis / Q000187:drug effects* / Q000276:immunology; D011550:Pseudomonas aeruginosa / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D037663:Pulmonary Surfactant-Associated Protein D; D011663:Pulmonary Surfactants / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats
D006023:Glycoproteins; D009895:Opsonin Proteins; D037663:Pulmonary Surfactant-Associated Protein D; D011663:Pulmonary Surfactants; D008320:Maltose