Pulmonary surfactant proteins A and D enhance neutrophil uptake of bacteria

Am J Physiol. 1998 Jun;274(6):L958-69. doi: 10.1152/ajplung.1998.274.6.L958.

Abstract

The collectins are a class of collagenous lectin proteins present in serum and pulmonary secretions [pulmonary surfactant protein (SP) A and SP-D] that are believed to participate in innate immune responses to various pathogens. With the use of flow cytometric and fluorescent-microscopic assays, SP-A and SP-D were shown to increase calcium-dependent neutrophil uptake of Escherichia coli, Streptococcus pneumoniae, and Staphylococcus aureus. Evidence is provided that the collectins enhanced bacterial uptake through a mechanism that involved both bacterial aggregation and direct actions on neutrophils. The degree of multimerization of SP-D preparations was a critical determinant of both aggregating activity and potency in enhancing bacterial uptake. The mechanisms of opsonizing activity of SP-D and SP-A differed in important respects from those of opsonizing antibodies. These results provide the first evidence that surfactant collectins may promote neutrophil-mediated clearance of bacteria in the lung independently of opsonizing antibody.

MeSH terms

  • Animals
  • Bacteria* / drug effects
  • Bacteria* / metabolism
  • Blood Bactericidal Activity*
  • Escherichia coli / drug effects
  • Escherichia coli / metabolism
  • Glycoproteins / metabolism
  • Glycoproteins / pharmacology*
  • Humans
  • Macromolecular Substances
  • Neutrophils / physiology*
  • Opsonin Proteins
  • Phagocytosis*
  • Proteolipids / metabolism
  • Proteolipids / pharmacology*
  • Pulmonary Surfactant-Associated Protein A
  • Pulmonary Surfactant-Associated Protein D
  • Pulmonary Surfactant-Associated Proteins
  • Pulmonary Surfactants / metabolism
  • Pulmonary Surfactants / pharmacology*
  • Rats
  • Recombinant Proteins / metabolism
  • Recombinant Proteins / pharmacology
  • Staphylococcus aureus / drug effects
  • Staphylococcus aureus / metabolism
  • Streptococcus pneumoniae / drug effects
  • Streptococcus pneumoniae / metabolism

Substances

  • Glycoproteins
  • Macromolecular Substances
  • Opsonin Proteins
  • Proteolipids
  • Pulmonary Surfactant-Associated Protein A
  • Pulmonary Surfactant-Associated Protein D
  • Pulmonary Surfactant-Associated Proteins
  • Pulmonary Surfactants
  • Recombinant Proteins