title: Surfactant protein D interacts with Pneumocystis carinii and mediates organism adherence to alveolar macrophages.
abstract: 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.
authors.affiliation: Thoracic Diseases Research Unit, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: O'Riordan
authors.forename: J E
authors.initials: JE
authors.lastname: Standing
authors.forename: K Y
authors.initials: KY
authors.lastname: Kwon
authors.forename: D
authors.initials: D
authors.lastname: Chang
authors.forename: E C
authors.initials: EC
authors.lastname: Crouch
authors.forename: A H
authors.initials: AH
authors.lastname: Limper
mesh_terms: D000818:Animals; D000946:Antigens, Fungal / Q000378:metabolism; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D050260:Carbohydrate Metabolism; D002448:Cell Adhesion; D005656:Fungal Proteins / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism*; D007150:Immunohistochemistry; D016676:Macrophages, Alveolar / Q000382:microbiology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D010587:Phagocytosis; D011010:Pneumocystis / Q000378:metabolism*; D011020:Pneumonia, Pneumocystis / Q000378:metabolism*; D011485:Protein Binding; D037663:Pulmonary Surfactant-Associated Protein D; D011663:Pulmonary Surfactants / Q000378:metabolism*; D051381:Rats
chemical_list: D000946:Antigens, Fungal; D005656:Fungal Proteins; D006023:Glycoproteins; D008562:Membrane Glycoproteins; D037663:Pulmonary Surfactant-Associated Protein D; D011663:Pulmonary Surfactants; C077556:GPA protein, Pneumocystis carinii sp.