[A new mechanism of bronchial hyperresponsiveness revealed by murine Th9 cell-transferred asthma model]

Bronchial asthma is a complex disease involving various inflammatory cells and tissue constituent cells. The spread of inhaled corticosteroids is changing asthma into a controllable disease, though the existence of intractable patients implies new mechanisms for the development and deterioration of asthma. Based on the difference in the pathological condition (phenotypes) and molecular mechanism (endotypes), subdivision of disease understanding is recently progressing. Accordingly, various T cell subsets other than Th2 cells, which have been considered to play a major role for many years, are being implicated in the pathogenesis of asthma. Therefore, we aimed to deepen the understanding of the complex mechanisms of intractable asthma by reviewing the characteristics of allergic inflammation mediated by each T cell subset and the trend of therapeutic strategies targeting their representative functional molecules. Among them, recently identified Th9 cells were reported to induce asthma-like eosinophilic inflammation with bronchial hyperresponsiveness (BHR). These phenotypes resemble to Th2 cells-mediated airway inflammation, though we found that Th9 but not Th2 cell-dependent asthma model develops eosinophil-independent and steroid-resistant BHR. Here, we would like to introduce our recent findings and an approach to elucidate a new mechanism of BHR, based on antigen-specific T cell subset-transferred mouse models we have established.