Surfactant abnormalities in idiopathic pulmonary fibrosis, hypersensitivity pneumonitis and sarcoidosis. A. Gu Ènther, R. Schmidt, F. Nix, M. Yabut-Perez, C. Guth, S. Rosseau, C. Siebert, F. Grimminger, H. Morr, H.G. Velcovsky, W. Seeger. #ERS Journals Ltd 1999. ABSTRACT: Bronchoalveolar lavage fluids (BALF) from patients with idiopathic pulmonary fibrosis (IPF; n=36), hypersensitivity pneumonitis (HP; n=32) and sarcoidosis (n=44) were investigated for their surfactant properties and compared to healthy control subjects (n=29).The phospholipid (PL) and protein concentration, the PL:protein ratio, PL subclasses, and the surfactant apoproteins (SP)A and SP-B were quantified in BALF. Large surfactant aggregates (LSA) were measured by means of ultracentrifugation and assayed for surface activity using the pulsating bubble surfactometer.As compared to controls, SP-A concentrations, LSA content and PL:protein ratios were significantly decreased in all groups, whereas PL and SP-B concentrations remained unchanged. Changes in the phospholipid profile, with reduced percentages of phosphatidylcholine (not significant) and phosphatidylglycerol and increased fractions of phosphatidylinositol and sphingomyelin (p<0.05), occurred more in IPF than in HP, and not in sarcoidosis. Surface activity was found to be severely impaired in IPF (minimum surface tension (cmin)~15±20 mN . m -1 ), but only modestly affected in HP and sarcoidosis (cmin~5 mN . m -1 ) compared to controls (cmin~0 mN . m -1 ). Reconstitution of pelleted surfactant material with soluble BALF proteins further increased cmin values.In conclusion, moderate changes in biochemical and physical surfactant properties are encountered in hypersensitivity pneumonitis and sarcoidosis, but pronounced disturbances occur in idiopathic pulmonary fibrosis.