ROLE OF INTERLEUKIN-2 IN THE DEVELOPMENT AND PERSISTENCE OF LYMPHOCYTIC ALVEOLITIS IN FARMERS LUNG

Farmer's lung (FL) is characterized by an intense lymphocytic alveolit is which persists after an acute episode with continuous exposure to t he offending antigens, This study aimed to examine the role of interle ukin-2 (IL-2) in the development and persistence of this lymphocytic a lveolitis. Three groups of dairy farmers were studied: acute FL, ex-FL (past history of FL but no clinical evidence of active disease) and a symptomatic farmers (no lung disease). IL-2 was measured by enzyme imm unosorbent assay and T-cell proliferation was evaluated by H-3-thymidi ne incorporation. Acute and ex-FL patients had more lymphocytes (p<0.0 1) and higher levels of IL-2 (p<0.05) in their bronchoalveolar lavage (BAL) than asymptomatic farmers, BAL lymphocytes from acute and ex-FL patients released considerable amounts of IL-2 after stimulation with concanavalin A and showed dose-dependent proliferative responses to IL -2. IL-2 production was decreased after treatment with predinisone. Ac ute FL patients, but not ex-FL, had higher levels of soluble CD25 in t heir serum than asymptomatics (p=0.009), These results suggest that in terleukin-2 may play a role in farmer's lung by providing a stimulus n ot only for the accumulation of lymphocytes but also for their persist ence at the site of hypersensitivity reaction, and that the lung is a likely source of this cytokine in vivo.