IMMUNOULTRASTRUCTURAL STUDY OF SURFACTANT SYSTEM - DISTRIBUTION OF SPECIFIC PROTEIN OF SURFACE-ACTIVE MATERIAL IN RABBIT LUNG

Abstract

Ducks were immunized with rabbit pulmonary surface active material that was prepared with Sephadex chromatographic separation of the lung washings. Specific antibody against a protein of surface active material was obtained after absorption of duck antisera with rabbit serum. Using the ultrastructural immunoperoxidase method, a dense reaction product was recognized in the alveolar lining material as granular deposits, closely associating with tubular myelin figures that were often observed in the basal layer of alveolar lining layer. In type I pneumocytes a reaction product was noted only in some pinocytotic vesicles. In type II pneumocytes there was an association with the lamellar inclusion bodies, multivesicular bodies, Golgi complex and endoplasmic reticulum. No reaction product was detected in bronchiolar and bronchial epithelial cells, including nonciliated bronchiolar and goblet cells. Specific protein in the surfactant is synthesized in type I pneumocytes and secreted into the alveolar space to become a part of the alveolar lining layer, thus suggesting that specific protein plays an important role in surfactant system. Reaction products could be detected in phagocytic vacuoles in alveolar macrophages and seem to be related to the clearance mechanism of the protein component of the surfactant.