Expanded peripheral CD62L^low inflammatory eosinophils in pediatric thunderstorm-related asthma exacerbations: A...

Thunderstorm-related asthma (TA) is a distinct environmental health emergency marked by abrupt surges in asthma exacerbations following thunderstorm events. Although peripheral eosinophilia has been implicated as a risk factor, the phenotypic and functional characteristics of eosinophils contributing to TA remain insufficiently defined. This study aimed to delineate the phenotypic characteristics of circulating eosinophil subsets in pediatric patients experiencing thunderstorm-related asthma exacerbations.

Children presenting with asthma exacerbations within 24 h of a documented thunderstorm event were enrolled as the TA group (n = 16), whereas age- and sex-matched children with well-controlled asthma served as controls (WA, n = 26). Circulating eosinophil subsets were characterized by flow cytometry, and type-2 cytokines and eosinophil-associated chemokines in serum were quantified by ELISA. In vitro, the blood eosinophils were isolated and stimulated with cytokines (IL-5, IL-3, and GM-CSF) to assess phenotypic changes and mediator secretion.

TA patients exhibited markedly higher levels of circulating CD62L^low inflammatory eosinophils (iEOS) compared with WA patients, which was closely correlated with clinical indicators of type-2 inflammation. Eosinophils from TA patients demonstrated broadly elevated expression of activation and cytokine receptor markers, including CD69, HLA-DR, CCR3, CD123, and CD125. Upon cytokine stimulation, the enriched eosinophils from TA patients exhibited a pronounced expansion of the CD62L^low subset with a reciprocal reduction in CD62L^bright cells, accompanied by elevated production of Eotaxin-1, Eotaxin-2, Eotaxin-3, and IL-13 in the culture supernatant.

Thunderstorm-related asthma is associated with a marked expansion of circulating CD62L^low iEOS that display heightened activation and cytokine responsiveness, indicating a primed type-2 inflammatory phenotype in susceptible children. Assessment of CD62L^low iEOS may be beneficial for early identification of children at high risk of thunderstorm-triggered exacerbations and help inform proactive preventive strategies.