Eosinophilic Bronchitis, Eosinophilia Associated Genetic Variants, and Notch Signaling in Asthma

While much has indeed been learned about the biology and role of eosinophils, the paradigm of eosinophils has the pros and cons in development of asthma. To answer the questions in the black box, this review firstly discusses the biological and morphological differences between asthma and eosinophilic bronchitis (EB). EB is an interesting clinical manifestation of eosinophilic airway disease that does not involve airway hyperresponsiveness (AHR), demonstrating that airway eosinophilia alone is insufficient to merit a diagnosis of asthma. Secondly, I will describe and discuss the effect(s) of single-nucleotide polymorphisms (SNPs) in the genes CCR3, IL-5 RECEPTOR ALPHA (IL5RA), and IL1RL1, and finally the in vitro and in vivo effects of Notch inhibition on both eosinophil differentiation and experimental asthma. Eosinophilic airway inflammation is not as important in the pathogenesis and maintenance of asthma as had previously been thought. However, the role of eosinophils in other asthma subphenotypes, including refractory or severely remodeled asthma, needs to be evaluated further. High-throughput methodologies such as genomics will facilitate the discovery of new markers of inflammation; these, in turn, will aid in the evaluation of the role of eosinophils in asthma and its various subphenotypes.