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Am J Physiol. 1999 Oct;277(4):L777-86. doi: 10.1152/ajplung.1999.277.4.L777.

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

Author information

1
Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.

Abstract

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.

PMID:
10516219
DOI:
10.1152/ajplung.1999.277.4.L777
[Indexed for MEDLINE]

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