Boonpiyathad T, et al. - Researchers determined how clinical and immunological response in asthma is influenced by high altitude therapy. Participants included hospitalized asthma patients (n=26) and healthy controls (n=9) in high-altitude for 21 days. Nine eosinophilic allergic (EA), 9 non-eosinophilic allergic and 8 non-eosinophilic non-allergic patients were included. Flow cytometry was used to evaluate eosinophils, T cells, Tregs, and innate lymphoid cells (ILC) from peripheral blood. Post-altitude therapy, a significant reduction in the number of eosinophils (both resting and activated) as well as CRTH2-expressing CD4⁺ and CD8⁺ T cells was observed in EA patients. In addition, altitude treatment resulted in a significant reduction in the frequency of CRTH2⁺ Tregs in all the asthma phenotypes as well as a significant attenuation in the frequency of ILC2 in EA. In this study, the observed consequences of asthma treatment in high altitude were attenuation in type 2 immune response, correction of the increased CRTH2 expression and its dysregulated functions.