Submucosal CD4+ and CD8+ T Lymphocyte Infiltrations in Asthma and Eosinophilic Bronchitis

Background: Asthma and eosinophilic bronchitis (EB) are eosinophilic inflammatory diseases of the airway. However, EB differs from asthma in that there is no variable airway obstruction or airway hyper-responsiveness. Pathologically, asthma is characterized by the accumulation of eosinophils and CD4+ T lymphocytes in the submucosa. A recent study showed that there was no significant difference between asthma and EB in terms of the submucosal eosinophil and T lymphocyte count. However, it is not known whether or not an infiltration of CD4+ and CD8+ T lymphocytes occurs in the airways of EB patients. The aim of this study was to identify the difference between the two conditions by measuring the submucosal CD4+ and CD8+ T lymphocyte count. Methods: Immunohistochemical analysis of bronchial-biopsy specimens was performed in 17 subjects with asthma and 24 subjects with EB. Results: The CD4+ T lymphocytes count in the asthma subjects and the EB subjects was similar (median, 58.6 vs 50.0 cells/mm², respectively; P=0.341). In contrast, the number of CD8+ T lymphocytes in the EB subjects was higher than that in the asthma subjects (median, 46.7 vs 11.8 cells/mm², respectively; P=0.003). Conclusion: The infiltration of submucosal CD8+ T lymphocytes may be associated with the pathophysiology of EB.