Evidence of ongoing mast cell and eosinophil degranulation in symptomatic asthma airway

Abstract

To assess whether mast cell and eosinophil (EOS) degranulation occurs in the airway of subjects with moderately symptomatic asthma, we have measured levels of preformed mast cell-derived mediators (histamine and tryptase) and EOS-derived mediators (major basic protein and EOS-derived neurotoxin) in bronchoalveolar lavage fluid (BALF) obtained from patients with symptomatic (N = 14) and asymptomatic asthma (N = 9) and patients without asthma (N = 6). Both the FEV1 (1.52 +/- 0.33 L:55% +/- 15% of predicted FEV1) and the forced expiratory flow at 50% (FEF50) (1.11 +/- 0.62 L/sec:26% +/- 14% of predicted FEF50) in the patients with symptomatic asthma were significantly lower than the corresponding values for FEV1 (3.16 +/- 0.45 L:86% +/- 10% of predicted FEV1) and the FEF50 (4.04 +/- 1.54 L/sec:71% +/- 25% of predicted FEF50) in the patients with asymptomatic asthma. Levels of histamine (4.8 +/- 5.0 ng/ml versus 0.2 +/- 0.2 ng/ml) (p = 0.05), EOS-derived neurotoxin (420.6 +/- 959.4 ng/ml versus 12.6 +/- 7.7 ng/ml) (p = 0.05), major basic protein (31.4 +/- 46.6 ng/ml versus less than 9 ng/ml) (p = 0.05), and percent EOSs (10.6% +/- 7.0% versus 1.1% +/- 0.9% of BAL cells) (p = 0.0006) were all significantly elevated in BALF from symptomatic compared to asymptomatic patients with asthma. The elevated levels of tryptase (13.2 +/- 14.8 ng/ml versus 3.9 +/- 3.9 ng/ml) in BALF from symptomatic compared to asymptomatic patients with asthma approximated, but did not reach, statistical significance. Spontaneous histamine release from BAL mast cells of symptomatic patients with asthma was 46% +/- 5% compared to 5% +/- 2% in asymptomatic patients with asthma. In response to antihuman IgE, histamine release from BAL mast cells recovered from asymptomatic patients with asthma increased to 25% +/- 10%, whereas in BAL mast cells of symptomatic patients with asthma, no anti-IgE potentiation of histamine release occurred. This study suggests that mast cell and EOS degranulation is ongoing in the airway of patients with moderately symptomatic asthma.