Surfactant protein D stimulates phagocytosis of Pseudomonas aeruginosa by alveolar macrophages

Am J Respir Cell Mol Biol. 1999 Nov;21(5):576-85. doi: 10.1165/ajrcmb.21.5.3334.


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.

Publication types

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

MeSH terms

  • Animals
  • Binding, Competitive / drug effects
  • Cells, Cultured
  • Dose-Response Relationship, Drug
  • Flow Cytometry
  • Glycoproteins / metabolism
  • Glycoproteins / pharmacology*
  • Hot Temperature
  • Macrophage Activation / drug effects
  • Macrophages, Alveolar / drug effects*
  • Macrophages, Alveolar / immunology
  • Macrophages, Alveolar / microbiology
  • Macrophages, Alveolar / ultrastructure
  • Male
  • Maltose / pharmacology
  • Microscopy, Electron
  • Microscopy, Fluorescence
  • Opsonin Proteins / pharmacology
  • Phagocytosis / drug effects*
  • Phagocytosis / immunology
  • Pseudomonas aeruginosa / cytology
  • Pseudomonas aeruginosa / immunology*
  • Pseudomonas aeruginosa / metabolism
  • Pulmonary Surfactant-Associated Protein D
  • Pulmonary Surfactants / metabolism
  • Pulmonary Surfactants / pharmacology*
  • Rats


  • Glycoproteins
  • Opsonin Proteins
  • Pulmonary Surfactant-Associated Protein D
  • Pulmonary Surfactants
  • Maltose