ENDOCRINE-CELLS IN DIFFUSE PULMONARY FIBROSIS

Background-There is evidence to suggest, particularly from studies in animals, that the products of pulmonary endocrine cells, especially ga strin releasing peptide, may have a role in the pathogenesis of fibros is in the lung. This study was carried out to examine the morphology, number, distribution, and content of pulmonary endocrine cells in tiss ue from 49 patients with diffuse pulmonary fibrosis. Methods-Twenty pa tients with interstitial pneumonitis, 17 with early fibrosis, and 12 w ith frank honeycombing were studied, together with five age matched co ntrols without pulmonary disease. Endocrine cells were immunolabelled by the avidin-biotin complex method for two general markers (protein g ene product 9.5 and neuron specific enolase) and a range of normal and aberrant secretory products. Results-In the early stages, characteris ed by vigorous pneumonitis, endocrine cells were normal in appearance and distribution but very few in number. They contained only those sec retory products normally found in such cells in health; inappropriate substances were not seen. By the time of early fibrosis endocrine cell s were even fewer. None were identifiable in the lungs affected by hon eycombing, despite the fact that all contained intact, well preserved epithelium. Conclusions-It seems unlikely that the products of pulmona ry endocrine cells can have any role in the pathogenesis of diffuse pu lmonary fibrosis in man, the diminution in their number with advancing fibrosis probably reflecting their loss simply as a consequence of ge neralised epithelial damage.