[Characteristics of airway inflammatory cells and mediators in eosinophilic bronchitis patients]

To investigate the features of airway inflammation in patients with eosinophilic bronchitis (EB) by analyzing the inflammatory cells and mediators in induced sputum and bronchoalveolar lavage fluid (BALF).

Sputum induced by hypertonic saline aerosol inhalation was collected in 43 patients with EB (EB group), 20 patients with cough variant asthma (CVA, CVA group), 16 patients with bronchial asthma (asthma group) and 21 healthy controls (healthy group). Bronchoalveolar lavage was also performed in 11 patients with EB and 10 patients with CVA. Differential cell count was carried out in sputum and BALF. Levels of eosinophilic cationic protein (ECP), leukotriene C(4) (LTC(4)) and histamine in sputum and BALF were measured.

The percentage of sputum eosinophils (EOS) showed significant difference among the four groups; healthy group 0.0020 +/- 0.0050, EB group 0.1130 +/- 0.1470, CVA group 0.1900 +/- 0.1800, asthma group 0.3860 +/- 0.2670 (P < 0.01). The difference between asthma group and CVA group, and the difference between CVA group and EB group were significant (P < 0.05). The percentage of EOS in BALF was (0.011 +/- 0.016) in EB group, (0.053 +/- 0.040) in CVA group, the difference being significant (P < 0.05). The concentration of sputum ECP was (0.62 +/- 0.66) mg/L in EB group, (1.27 +/- 1.74) mg/L in CVA group, (0.07 +/- 0.10) mg/L in healthy group, the difference among the three groups being significant (P < 0.01). The difference of LTC(4) level was also significant when CVA group (0.65 +/- 0.62) microg/L was compared with EB group (0.39 +/- 0.61) microg/L (P < 0.05) and healthy group (0.15 +/- 0.11) microg/L (P < 0.01). The difference of histamine level in the supernatant of BALF was significant between CVA group (3.4 +/- 1.4) microg/L and EB group (1.6 +/- 1.5) microg/L (P < 0.05).

EOS infiltration is mainly localized to the central airway in EB, with lower airway levels of LTC(4) and histamine as compared to CVA. These inflammatory features may partly explain the absence of non-specific airway hyperresponsiveness in patients with EB.