Surfactant Protein D Interacts With Pneumocystis Carinii and Mediates Organism Adherence to Alveolar Macrophages

J Clin Invest. 1995 Jun;95(6):2699-710. doi: 10.1172/JCI117972.


Pneumocystis carinii interacts with glycoproteins present in the lower respiratory tract through its mannose-rich surface antigen complex termed gpA. Surfactant protein D (SP-D) is a recently described component of the airspace lining material that possesses a calcium-dependent lectin domain capable of interacting with glycoconjugates present on microorganisms and leukocytes. Accordingly, we evaluated the extent and localization of SP-D in the lower respiratory tract during Pneumocystis pneumonia in an immunosuppressed rat model and examined its role in modulating interaction of P. carinii with macrophages. We report that SP-D is a major component of the alveolar exudates that typify P. carinii pneumonia and is present bound to the surface of P. carinii organisms in vivo. We further demonstrate that SP-D binds to P. carinii through saccharide-mediated interactions with gpA present on the surface of the organism. Lastly, we show that SP-D augments binding of P. carinii to alveolar macrophages, but does not significantly enhance macrophage phagocytosis of the organism. The interaction of SP-D with gpA represents an additional important component of the host-parasite relationship during P. carinii pneumonia.

Publication types

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

MeSH terms

  • Animals
  • Antigens, Fungal / metabolism
  • Bronchoalveolar Lavage Fluid / chemistry
  • Carbohydrate Metabolism
  • Cell Adhesion
  • Fungal Proteins / metabolism
  • Glycoproteins / metabolism*
  • Immunohistochemistry
  • Macrophages, Alveolar / microbiology*
  • Membrane Glycoproteins / metabolism
  • Phagocytosis
  • Pneumocystis / metabolism*
  • Pneumonia, Pneumocystis / metabolism*
  • Protein Binding
  • Pulmonary Surfactant-Associated Protein D
  • Pulmonary Surfactants / metabolism*
  • Rats


  • Antigens, Fungal
  • Fungal Proteins
  • Glycoproteins
  • Membrane Glycoproteins
  • Pulmonary Surfactant-Associated Protein D
  • Pulmonary Surfactants
  • GPA protein, Pneumocystis carinii sp.