AIRWAY EOSINOPHILIA AND EXPRESSION OF INTERLEUKIN-5 PROTEIN IN ASTHMAAND IN EXACERBATIONS OF CHRONIC-BRONCHITIS

Background An increased number of eosinophils in the bronchial mucosa has been demonstrated both in asthma and in exacerbations of chronic b ronchitis. Objective To investigate whether the airway eosinophilia pr esent in asthma and in chronic bronchitis during exacerbations is asso ciated with interleukin (IL)-5 protein expression in the bronchial muc osa. Methods We obtained bronchial biopsies in 18 subjects with asthma (four intrinsic, seven extrinsic and seven occupational) and in 11 su bjects with chronic bronchitis examined during an exacerbation. The fi ndings were compared with those of bronchial biopsies from 10 subjects with chronic bronchitis examined under baseline conditions and from s even normal subjects, taken as controls. By immunohistochemistry, we a ssessed the expression of IL-5 protein and the number of eosinophils ( EG2), mast cells (tryptase), and T-lymphocytes (CD3) in the submucosa. Results As compared with controls, the number of eosinophils was incr eased to a similar degree in both asthma (P < 0.001) and in exacerbati ons of chronic bronchitis (P < 0.001), whereas the number of IL-5 immu nopositive cells was increased significantly only in asthma (P < 0.01) . No differences were observed in the number of mast cells and T-lymph ocytes between the four groups of subjects examined. Conclusions This study shows that the degree of airway eosinophilia is similar in asthm a and in exacerbations of chronic bronchitis, but only in asthma is it associated with an increased expression of IL-5 protein in the bronch ial mucosa.