SP-A enhances phagocytosis of Klebsiella by interaction with capsular polysaccharides and alveolar macrophages

Kisra Kabha, Jutta Schmegner, Yona Keisari, Haralambos Parolis, Jutta Schlepper-Schaefer, Itzhak Ofek

Research output: Contribution to journalArticlepeer-review

Abstract

We found that surfactant protein A (SP-A) enhances phagocytosis of Klebsiella pneumoniae K21a but not of K2 serotypes by alveolar macrophages. SP-A interacted with the capsule of K21a (containing Manα1Man sequences) as shown by SP-A-induced agglutination of the bacteria, by binding of SP-A- coated particles onto the bacterial surface, and by binding of SP-A to immobilized parent K21a strain and recombinant strains that switched their capsule from K2 to K21a. In contrast, only marginal binding of SP-A to K2 parent strain (lacking this sequence) could be detected. Furthermore, binding of capsular polysaccharide of K21a to immobilized SP-A was inhibited by mannan but not by lipopolysaccharide and K2 capsular polysaccharide. SP-A- treated macrophages bound increased numbers of parent K21a strain and recombinant strains of K21a capsule type but considerably less parent K2 strain. SP-A also enhanced killing of K21a strains by macrophages. The enhanced binding of K21a by macrophages pretreated with SP-A was inhibited by mannan, suggesting that binding is mediated by the mannose receptor on macrophages. We conclude that SP-A increases phagocytosis of the Klebsiella by two mechanisms, one of which is by serving as an opsonin, which binds to the capsular polysaccharides of the bacteria and potentially to SP-A receptors on the macrophages, and the other by activating the macrophages, resulting in increased activity of the mannose receptor.

Original languageEnglish
Pages (from-to)L344-L352
JournalAmerican Journal of Physiology - Lung Cellular and Molecular Physiology
Volume272
Issue number2 16-2
DOIs
StatePublished - Feb 1997

Keywords

  • Klebsiella pneumoniae
  • mannose receptor
  • surfactant protein A
  • surfactant protein A receptor

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