Reply: Elevated Sputum IL-5 and Submucosal Eosinophilia in Obese Individuals with Severe Asthma

摘要

The letters from van der Wiel and colleagues and Marijsse and colleagues provide further evidence that the relationship between blood, bronchial submucosal, and airway luminal eosinophilic inflammation is different in subjects with asthma with and without obesity. We described in severe asthma elevated sputum IL-5 and bronchial eosinophilic inflammation in obese subjects with asthma without an associated increase in blood or sputum eosinophils. van der Wiel and colleagues extend this finding to demonstrate that the number of eosinophils in the bronchial submucosa is increased in obese subjects with mild-to-moderate asthma, whereas Marijsse and colleagues provided further evidence that sputum IL-5 mRNA is increased in obese subjects with asthma without an increase in mRNA for other T helper type 2 cytokines. In these and previous studies, asthma associated with obesity is consistently characterized by an absence of a sputum eosinophilia. The apparent paradox between tissue and luminal eosinophilic inflammation remains inadequately explained. In our report, we were unable to demonstrate increased macrophage uptake of luminal eosinophils, suggesting that the increased number in the tissue is due to increased retention in the lumen wall, rather than more eosinophils trafficking from blood through the airway wall into the lumen with increased phago/efferocytosis of luminal eosinophils.