Interleukin-2 and soluble interleukin-2 receptor in bronchoalveolar lavage fluid from patients with bronchial asthma

To clarify the interrelation between interleukin-2 (IL-2) and soluble IL-2R receptor (sIL-2R), as products of T-cell activation in the bronchial tree of patients with bronchial asthma, we measured the concentration of IL-2, sIL-2R, and the cellular composition in bronchoalveolar lavage (BAL) fluid. We also measured physiologic parameters, including provocation concentration of histamine required to reduce the forced expiratory volume in 1 s by 20 percent of the prechallenge baseline (PC20). The concentrations of IL-2 and sIL-2R were higher in BAL fluid of symptomatic patients with bronchial asthma than those of normal subjects and asymptomatic patients. There was a significant correlation between IL-2 and sIL-2 concentrations in BAL fluid of the patients with bronchial asthma. Patients with other lung diseases had significantly higher concentration of IL-2 than normal control; however, sIL-2R was not detected in their BAL fluids. The concentration of IL-2 inversely correlated with FEV1 in symptomatic bronchial asthma. Among the inflammatory cells in BAL fluid, percentages of eosinophils showed significant correlation with the concentrations of IL-2 and sIL-2R in BAL fluid of the patients with bronchial asthma. In conclusion, IL-2 within the bronchial tree appears to be associated with eosinophil infiltration. This leads to physiologic changes in symptomatic patients with bronchial asthma, which may be influenced by the presence of sIL-2R in BAL fluid.