Granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3) are hematopoietic growth factors that have been shown to induce proliferation and activation of inflammatory cells, and may play a role in allergic reactions. Since little is known about the involvement of cytokines in allergic inflammation in the lung, the levels of GM-CSF and IL-3 were measured in bronchoalveolar lavage (BAL) fluids obtained in the late phase after segmental lung antigen (Ag) challenge in 14 allergic rhinitis subjects with or without bronchial asthma. BAL fluids either after Ag (ragweed, dust mite, or timothy) or saline control challenge were recovered 19 h later. In 6 of the 14 patients, BAL fluids were concentration-dialyzed (20x) and assayed for cytokine activity. Cytokine assays were performed using the human megakaryocytic leukemic cell line M-07e, which is responsive to either GM-CSF or IL-3. The level of GM-CSF-equivalents was approximately 25 times higher in Ag-challenged sites (49.9 +/- 12.7 pg/ml; mean +/- SEM), compared to saline challenge sites (2.2 +/- 1.0, p < 0.01, n = 9). Neutralization experiments using a polyclonal specific antibody (Ab) against GM-CSF and IL-3 revealed that the bulk of the activity was GM-CSF. BAL fluids from Ag- and saline-challenged sites in one nonatopic subject contained no significant GM-CSF activity. Furthermore, the level of GM-CSF in Ag-challenged BAL fluid and the percentage of eosinophils in BAL from each subject correlated significantly (r = 0.73, p < 0.005, n = 14).(ABSTRACT TRUNCATED AT 250 WORDS)