Background: To elucidate the role of T-cell activation in the physiologic changes and cellular infiltrations in the bronchial tree of patients with symptomatic bronchial asthma, we measured the concentration of soluble interleukin-2 receptor (sIL-2R), cellular compositions and IL-2R expression on cells in bronchoalveolar lavage (BAL) fluid. We also measured physiologic parameters, including a provocation concentration of histamine required to reduce the forced expiratory volume in 1 second by 20% of the prechallenge baseline (PC20).
Results: The concentration of sIL-2R and the ratio of IL-2R expression on CD3 positive lymphocytes were significantly higher in BAL fluid from 20 patients with symptomatic bronchial asthma than concentrations in fluid from nine healthy controls (p < 0.01) and six asymptomatic patients with bronchial asthma (p < 0.05). The concentration of sIL-2R correlated with the percentage of IL-2R expression on CD3 positive lymphocytes (rs = 0.709, p < 0.01). There was no difference in sIL-2R concentration of BAL fluid between the healthy control and the patient with asymptomatic bronchial asthma. Among the inflammatory cells recovered in BAL fluid, the percentages of eosinophils showed significant positive correlation with the concentration of sIL-2R in BAL fluid in the patients with bronchial asthma. The concentration of sIL-2R significantly correlated with forced expiratory volume one second, peak expiratory flow rate, and PC20 when observed in all study subjects, but not in the patients with bronchial asthma.
Conclusion: We conclude that T-cell activation within the bronchial tree appears to have a role in the infiltration of eosinophils into the bronchial tree, which may lead to enhanced bronchial hyperreactivity in patients with bronchial asthma.