Surfactant Protein A Enhances Alveolar Macrophage Phagocytosis of a Live, Mucoid Strain of P. Aeruginosa

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

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cell Adhesion
  • Cell Membrane / metabolism
  • Macrophages, Alveolar / drug effects*
  • Macrophages, Alveolar / physiology*
  • Macrophages, Alveolar / ultrastructure
  • Male
  • Microscopy, Electron
  • Phagocytosis / drug effects*
  • Proteolipids / metabolism
  • Proteolipids / pharmacology*
  • Pseudomonas aeruginosa / metabolism
  • Pseudomonas aeruginosa / physiology*
  • Pulmonary Surfactant-Associated Protein A
  • Pulmonary Surfactant-Associated Proteins
  • Pulmonary Surfactants / metabolism
  • Pulmonary Surfactants / pharmacology*
  • Rats

Substances

  • Proteolipids
  • Pulmonary Surfactant-Associated Protein A
  • Pulmonary Surfactant-Associated Proteins
  • Pulmonary Surfactants