An immunohistochemical study of bronchial cells producing surfactant protein A in the developing human fetal lung

A study on immunohistochemical localization of pulmonary surfactant protein A (SP-A) in the developing human fetal lung was performed using a monoclonal antibody, PE10, against human SP-A. At 21 weeks of gestation, a few bronchial cells positive to PE10 were observed to be scattered in the main and segmental bronchi. The number of these cells appears to increase until the 32nd week of gestation, and then decrease thereafter, almost disappearing by 39 weeks. On the other hand, alveolar type II cells and Clara cells positive to PE10 began to appear at 29 weeks, increase in number until around 39 weeks, and remain constant throughout adulthood. A few bronchial glandular cells positive to PE10 were still noticed in the fetal lung. This is the first report of the presence of SP-A-containing cells in the fetal lung. This is the first report of the presence of SP-A-containing cells in the human fetal bronchial epithelium (not Clara cells in the terminal bronchiolus), proving the regularity of the sequential distribution of SP-A-containing cells in the bronchoalveolar system during pulmonary development.