[Bronchial asthma as an inflammation and the use of inhaled steroid]

Recently, bronchial asthma has been widely recognized as a chronic inflammatory disorder of the airways. In the course of inflammation, many kinds of inflammatory cells such as lymphocytes, especially Th2 lymphocytes, mast cells, eosinophills, bronchial epithelial cells interact each other by so-called cytokine network. Bronchial hyperreactivity, which is a characteristic phenomenon in bronchial asthma, is induced as a result of bronchial inflammation. According to the inflammation theory of pathogenesis of bronchial asthma, anti-inflammatory treatment using inhaled corticosteroid is recommended as the first choice of asthma therapy. Bronchial biopsy proved decrease of the number of infiltrating inflammatory cells such as T lymphocytes, eosinophils and mast cells in the bronchial submucosal tissue after inhaled steroid treatment. Improvement of bronchial reactivity after inhaled steroid therapy was also reported. Recently, a certain group of so-called steroid resistant asthma has been known and the mechanism of it is now under investigation.