EOSINOPHILIC INFLAMMATION IN ASTHMA

The importance of eosinophils in the pathogenesis of bronchial asthma is not established. In an attempt to evaluate the role of eosinophilic inflammation in asthma, we compared 10 normal subjects with 43 patients with chronic asthma, 19 of whom had severe disease as assessed by a clinical scoring method described by Aas and by pulmonary-function tests. Eosinophils were counted in peripheral blood and bronchoalveolar-lavage fluid, and in biopsy specimens obtained from the patients and post mortem from 8 subjects without asthma, but not from the 10 normal controls. Eosinophil cationic protein was titrated by radioimmunoassay in the bronchoalveolar-lavage fluid from all subjects and studied by immunohistochemistry in the biopsy specimens. There was a significant increase in the number of peripheral-blood eosinophils in the patients that was correlated with the clinical severity of asthma (P<0.001) and pulmonary function (P<0.03). Levels of eosinophils and eosinophil cationic protein were increased in the bronchoalveolar-lavage fluid from the patients and were also correlated with the severity of asthma (P<0.001 and P<0.002, respectively). Hematoxylin–eosin staining of bronchial-biopsy specimens showed that intraepithelial eosinophils were present only in patients with asthma. Immunohistochemical analysis of eosinophil cationic protein revealed that normal subjects had only a few nondegranulated eosinophils deep in the submucosa, whereas all the patients had degranulated eosinophils beneath the basement membrane and among epithelial cells. In some patients there was a relation between the presence of degranulated eosinophils and epithelial damage. Eosinophilic inflammation of the airways is correlated with the severity of asthma. These cells are likely to play a part in the epithelial damage seen in this disease. (N Engl J Med 1990; 323:1033–9.) THE most characteristic feature of asthma is bronchial inflammation leading to nonspecific hyper-reactivity.1 The association between eosinophilia and asthma was observed shortly after eosinophils were first described,2 and the view that eosinophils are predominant among the cells involved in the inflammation in asthma is accepted, although there are discordant observations.3 In patients with asthma, eosinophils are present in increased numbers in blood4,5 and are found in sputum6,7 and bronchoalveolar-lavage fluid.8,9 Histologic studies have shown that eosinophils are often observed in the bronchial submucosa of patients who have died of asthma attacks.2,10 11 12 13 14 15 16 17 18 19 20 21 After bronchial challenge with an allergen, in patients in. © 1990, Massachusetts Medical Society. All rights reserved.