Bronchoalveolar mast cells in normal farmers and subjects with farmer's lung. Diagnostic, prognostic, and physiologic significance.

To evaluate the specificity and significance of increased lavage mast cells in farmer's lung, we examined the lavage cell differentials of 89 farmers and 19 normal nonfarming control subjects. The farmers were divided into four groups: acute farmer's lung (n = 17), farmers with one or more prior episodes of farmer's lung who remained in daily contact with hay (n = 26) or quit farming (n = 14), and normal farmers (n = 36). A total of 14 of the subjects with prior episodes of farmer's lung and still farming and 15 normal farmers were evaluated twice at a 2-yr interval. The lavage mast cell numbers were significantly higher in acute farmer's lung (7.5 +/- 7.3 x 10(3)/ml, mean +/- SD) and ex-farmer's lung who were still farming (1.2 +/- 1.3 x 10(3)/ml) than in normal farmers (0.1 +/- 0.1 x 10(3)/ml) (p less than 0.01). A total of 8 of 14 exfarmer's lung patients who had quit farming and 18 of 36 normal farmers had an increased number of mast cells in lavage, but mast cell count never exceeded 0.5% of total recovered cells. In the acute farmer's lung and ex-farmer's lung-still farming groups, the mast cell count correlated with the lymphocyte count: r = 0.83 and r = 0.69 (p less than 0.001), respectively. In the two groups evaluated twice, mast cell numbers at the first study did not correlate with changes seen at the second study in chest roentgenogram and pulmonary functions. We conclude that an increase in lavage mast cells occurs commonly as a part of the immune response against thermophilic bacteria.(ABSTRACT TRUNCATED AT 250 WORDS)