Abstract
Asthma, a chronic respiratory disease involving variable airflow limitations, exhibits two phenotypes: eosinophilic and neutrophilic. The asthma phenotype must be considered because the prognosis and drug responsiveness of eosinophilic and neutrophilic asthma differ. CD4+ T cells are the main determinant of asthma phenotype. Th2, Th9 and Tfh cells mediate the development of eosinophilic asthma, whereas Th1 and Th17 cells mediate the development of neutrophilic asthma. Elucidating the biological roles of CD4+ T cells is thus essential for developing effective asthma treatments and predicting a patient’s prognosis. Commensal bacteria also play a key role in the pathogenesis of asthma. Beneficial bacteria within the host act to suppress asthma, whereas harmful bacteria exacerbate asthma. Recent literature indicates that imbalances between beneficial and harmful bacteria affect the differentiation of CD4+ T cells, leading to the development of asthma. Correcting bacterial imbalances using probiotics reportedly improves asthma symptoms. In this review, we investigate the effects of crosstalk between the microbiota and CD4+ T cells on the development of asthma.
Highlights
Thorburn et al reported that pregnant mother mice fed a high-fiber diet exhibited increased acetate production, which in turn increased the number of Tregs via HDAC9 inhibition; this led to alleviation of house dust mites (HDMs)-induced eosinophilic inflammation [139]
Th2, Th9, and T follicular helper cell (Tfh) cells are involved in the development of eosinophilic asthma, whereas Th1 and Th17 cells are involved in the development of neutrophilic asthma
Proper classification of the asthma phenotype based on CD4+ T cells is essential to determine the optimal asthma treatment and accurately predict the prognosis
Summary
Asthma is a common respiratory disease involving chronic airway inflammation, primarily caused by allergens such as house dust mites (HDMs), pollen, and animal dander [1]. A variety of drugs for treating severe asthma have been developed in recent years, including mepolizumab, reslizumab, benralizumab and dupilumab [6]. These drugs were developed for patients with T helper (Th) asthma, and no drugs for patients with non–Th2-asthma are currently available. Is responsive to steroid treatment, and severe eosinophilic asthma is effectively treated by various newly developed drugs [5]. Non-Th2 asthma (i.e., neutrophilic asthma), by contrast, is characterized by neutrophilic infiltrate in the sputum [7] and secretion of high levels of interferon gamma (IFN-γ) and IL-17 by Th1 and Th17 cells. We discuss the role of the bacterial microbiota in the induction of asthma and its effect on CD4+ T cells in asthma
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