Pigeon breeder's disease: Immunofluorescence and ultrastructural observations

Open lung biopsy specimens were obtained from 36 patients with proven extrinsic allergic alveolitis due to exposure to pigeon droppings. Histologic examination disclosed an interstitial infiltrate composed of lymphocytes, few plasma cells, and occasional giant cells. Intraalveolar macrophages with foamy cytoplasm were seen in 18 patients. Immunofluorescence examination disclosed IgG in alveolar walls in a granular pattern in 12 patients and associated with plasma cells. Complement components were present in only 2 patients. Tests for IgD were negative in all cases. There were scattered granules of IgA in some airways in 11 patients. Fibrinogen was found in 24 biopsies. Electron microscopic examination demonstrated irregular thickening of alveolar septa. Epithelial damage and desquamation of type II cells were seen in patients with a history of recent exposure. Basement membranes in some areas showed marked thickening and duplication. We did not find ultrastructural evidence of immune complexes in basement membranes. Mast cells were increased in number in all biopsies and were prominent in perivascular connective tissue and in close association with areas of fibrosis. Complement components were found in only 1 biopsy. This suggests that the presence of fibrin and fibrinogen is due to the inflammatory response.