Immunohistochemical study of human pulmonary surfactant apoproteins with monoclonal antibodies. Pathologic application for hyaline membrane disease.

Three monoclonal antibodies, PC6, PE10, and PE12, were used for immunohistochemical studies of human lungs by immunoperoxidase staining. Monoclonal antibodies PC6 and PE10 against pulmonary surfactant apoproteins stained faint granules in the cytoplasm of some alveolar wall cells in adult lung. These stained cells appeared to be alveolar Type II cells. A fetal lung of 20 weeks' gestation had no any positive staining. However, a few scattered positive cells were observed in a newborn lung of 31 weeks' gestation, and the stained cells increased progressively with increasing gestational age. The positively stained cells were very few in the lungs of newborns who died of respiratory distress syndrome (RDS), but the lungs of newborns who died of other causes after recovery from RDS showed many positively stained cells. These results suggest that the immunohistochemical demonstration of the monoclonal antibodies PC6 and PE10 could be a good pathodiagnostic indicator reflecting the localization and development of pulmonary surfactant by alveolar Type II cells. On the other hand, monoclonal antibody PE12 was found to recognize the antigen that occurs on the surfaces of the alveoli of fetal, newborn, and adult lungs as one component of the alveolar lining layer, different from pulmonary surfactant.