Fibrogenic activities in bronchoalveolar lavage fluid of farmer's lung.

Hyaluronic acid (HA), type III procollagen, fibronectin, and fibroblast growth factors (FGF) were measured in 43 bronchoalveolar lavage fluid (BALF) specimens obtained from 38 patients with farmer's lung (FL) and in BALF of 9 nonexposed normal control subjects. Bronchoalveolar lavage was done in 21 farmers with acute FL (acute) and in 22 with a history of previous FL (Ex) who were still in daily contact with dairy barns. All farmers from the acute and Ex groups had a lymphocytic alveolitis, respectively, 62.7 (3.5) percent (mean [SEM]) and 48.1 (4.3) percent. Hyaluronic acid, type III procollagen, fibronectin, and FGF were all highly increased in acute disease. These substances were also increased in the BALF of subjects of the Ex group who had no clinical symptoms or signs of acute disease at the time of lavage, but were actively farming. The increase in type III procollagen, however, was less in this group than in the subjects with acute disease. These observations suggest that the fibrosing activities and potentialities of the allergic alveolitis of FL are fully expressed at the time of clinical presentation and also in the subclinical phase of the disease in susceptible farmers who remain exposed after an initial acute phase of the disease.