Mast cells in bronchoalveolar lavage fluid and in transbronchial biopsy specimens of patients with farmer's lung disease.

Recently, an increased number of mast cells have been reported in bronchoalveolar lavage fluid (BAL) of patients with farmer's lung disease. Some authors pointed out the pathogenetic importance of mast cells in farmer's lung on the basis of their correlation with the activity of the disease, with the BAL lymphocyte counts, and with the markers of lung fibrosis. To determine whether BAL reflects the histologic aspects of the lung histologic features in patients with farmer's lung disease, mast cells recovered from lavage fluid were compared with tissue sections from transbronchial lung biopsies in 15 patients. Mast cell counts in BAL and lung biopsy specimens were significantly correlated (r = 0.88; p less than 0.01), while no other correlations between BAL inflammatory cells and tissue mast cells were found. In lung tissue, there were four times the increased number of mast cells in respect to the control group (84.4 +/- 28.8 vs 20.4 +/- 13.4 mast cells per square millimeter); 83.2 percent of mast cells were found in the alveolar septa, 14.9 percent within alveoli, 0.7 percent among alveolar lining cells, and 1 percent along blood vessels. No mast cells were located within alveoli in controls. In BAL, only lymphocyte and mast cell counts (56.4 +/- 18.6 percent, p less than 0.001; 3.9 +/- 1.5 5 percent, p less than 0.001, respectively) were significantly increased. Our data suggest that in farmer's lung disease, BAL correctly samples the alveolitis. Mast cells, such as lymphocytes, seem to be primary inflammatory cells involved at the site of the disease activity.