Surfactant protein-D and pulmonary host defense.
Surfactant protein-D (SP-D) participates in the innate response to inhaled microorganisms and organic antigens, and contributes to immune and inflammatory regulation within the lung. SP-D is synthesized and secreted by alveolar and bronchiolar epithelial cells, but is also expressed by epithelial cells lining various exocrine ducts and the mucosa of the gastrointestinal and genitourinary tracts. SP-D, a collagenous calcium-dependent lectin (or collectin), binds to surface glycoconjugates expressed by a wide variety of microorganisms, and to oligosaccharides associated with the surface of various complex organic antigens. SP-D also specifically interacts with glycoconjugates and other molecules expressed on the surface of macrophages, neutrophils, and lymphocytes. In addition, SP-D binds to specific surfactant-associated lipids and can influence the organization of lipid mixtures containing phosphatidylinositol in vitro. Consistent with these diverse in vitro activities is the observation that SP-D-deficient transgenic mice show abnormal accumulations of surfactant lipids, and respond abnormally to challenge with respiratory viruses and bacterial lipopolysaccharides. The phenotype of macrophages isolated from the lungs of SP-D-deficient mice is altered, and there is circumstantial evidence that abnormal oxidant metabolism and/or increased metalloproteinase expression contributes to the development of emphysema. The expression of SP-D is increased in response to many forms of lung injury, and deficient accumulation of appropriately oligomerized SP-D might contribute to the pathogenesis of a variety of human lung diseases.
Crouch
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Department of Pathology and Immunology, Washington University School of Medicine, St Louis, Missouri, USA. crouch@path.wustl.edu
D000818:Animals; D001419:Bacteria / Q000378:metabolism; D005658:Fungi / Q000378:metabolism; D014644:Genetic Variation; D006801:Humans; D008024:Ligands; D008168:Lung / Q000276:immunology*; D008954:Models, Biological; D037663:Pulmonary Surfactant-Associated Protein D / Q000737:chemistry / Q000502:physiology*; D014780:Viruses / Q000378:metabolism
D008024:Ligands; D037663:Pulmonary Surfactant-Associated Protein D