Pathological features of airway inflammation in eosinophilic bronchitis

AIM: To explore the pathological features of airway inflammation in patients with eosinophilic bronchitis (EB) and compared to those with cough variant asthma (CVA). METHODS: Flexible fibre optic bronchoscopy was performed in 11 patients with EB, 10 with CVA, 14 with bronchial asthma and 10 normal controls. The mean thickness of the basement membrane was measured by light microscopy. Using immunohistochemical and special staining, the localization and density of inflammatory cells (eosinophils, mast cells, T lymphocytes) were detected in bronchial submucosa in EB and CVA patients. RESULTS: The mean thickness of the basement membrane was significantly increased in the subjects with EB ［2.92 μm (2.10-6.50 μm)］, CVA ［5.64 μm (3.23-8.48 μm)］ and bronchial asthma ［9.08 μm (6.61-11.99 μm)］ rather than that in the normal controls ［2.08 μm (1.62-3.40 μm)］. There were also significant differences among the three groups. The number of mast cells and eosinophils in the bronchial submucosal from subjects with EB ［75 cells/mm2 (35-112 cells/mm2), 7 cells/mm2 (0-31 cells/mm2)］ was substantially decreased than those in subjects with CVA ［148 cells/mm2 (34-200 cells/mm2), 114 cells/mm2 (1-768 cells/mm2); P<0.05］. There was no significantly difference in T lymphocyte counts between the EB and CVA. CONCLUSIONS: EB is an inflammatory disorder of the airways with the characteristics of various inflammatory cell (eosinophils, mast cells and T lymphocytes) infiltration. The mean thickness of the basement membrane is less severe than that in CVA and bronchial asthma and the level of infiltration of inflammatory cells is less than that in CVA, which may be one of the reasons that airway hyperresponsiveness is rarely seen in EB.