文本框: Antiinflammatory Properties of Natural Surfactant Preparations Christian P. Speer, University Children’s Hospital, Würzburg, Germany Surfactant replacement therapy in severe neonatal respiratory distress syndrome (RDS) effectively reduces acute pulmonary morbidity and mortality in preterm infants. Immediately after intrabronchial instillation of natural surfactant preparations, there is a dramatic increase in oxygenation with subsequent reduction in ventilatory requirements. Besides these biophysical properties there is growing evidence that natural surfactant preparation may exert various effects on neutrophils, monocytes and macrophages which are accumulating within the airspace of infants with RDS. These cells have an essential role in the inflammatory response and in the regulation of immune functions as well as in pulmonary host defense. Natural surfactant preparations which have been derived from bovine and porcine lungs contain the surfactant-associated hydrophobic proteins SP-B and SP-C; these proteins facilitate the adsorption and spreading of phospholipids. The hydrophilic proteins SP-A and SP-D, however, are removed during the extraction process. Besides improving surface properties and regulating secretion and recycling of surfactant constituents by alveolar cells, SP-A and SP-D seem to play a role in host defense mechanisms and immunoregulation. Pulmonary surfactant is a complex mixture of phospholipids, and neutral lipids. Phosphatidylcholine is the major component, constituting about 60% of total phospholipids and dipalmitoylphosphatidylcholine (DPPC) is the primary surface tension lowering phospholipid. Natural surfactant preparations vary in composition of phospholipids, concentration and volume. A number of experimental data indicate that lipid components of natural surfactant preparations are able to modify or suppress a variety of immune cell functions. Most of these investigations have been carried out with cells isolated from lung lavage material, with cell lines or peripheral blood cells from different species. Adhesiveness of phagocytes exposed to natural surfactant was found to be slightly impaired, whereas chemotaxis of monocytes and macrophages was unaffected by surfactant. Phagocytosis and killing of various bacteria by surfactant-treated phagocytes was found to be normal or slightly decreased. The generation of toxic oxygen radicals, however, was decreased in neutrophils, monocytes and alveolar macrophages exposed to natural surfactant preparations. Recent findings suggest that the mechanism of phospholipid induced inhibition of O2--production by phagocytes involves attenuation of translocation of cytosolic "respiratory burst oxidase" components to the plasma membrane. In addition, the release of lipid mediators by inflammatory cells was effectively suppressed during surfactant……