Eosinophil migration is enhanced towards IL-5 and eotaxin in COPD

Introduction: Eosinophilic COPD is an important inflammatory phenotype, but the mechanism is unknown. In this study we examine the migration of eosinophils in different inflammatory COPD phenotypes towards IL-5 and eotaxin which was unelucidated. Methods: Whole blood from 4 eosinophilic COPD patients, 4 non-eosinophilic COPD patients and 6 healthy controls was collected, with eosinophils isolated by ficoll-paque and dextran Methods Eosinophils were assessed for chemotactic ability. Briefly, eosinophils re-suspended at 1 χ 105 cells/ml were placed on a 3 µm pore membrane above solutions of IL-5 and eotaxin (50 ng/ml and 10 ng/ml respectively for one hour). Cells which passed through the membrane were treated with Cell-Titer-Glo solution to allow their detection by plate reader. Eosinophilic COPD was defined as patients with a peripheral blood eosinophil count of ≥2% of white blood cells. Results: Eosinophils from eosinophilic COPD patients showed significantly greater migration than both healthy controls towards IL-5 (median: 7021 cells, IQR: 6098–10 013 v median: 2288 cells, IQR: 1389–2702, p=0.0095) and non-eosinophilic COPD patients, (median: 3219 cells, IQR: 2488–3785, p=0.0286). Eosinophils from eosinophilic and non-eosinophilic patients (median: 5363 cells, IQR: 4101–5420 and median: 3683, IQR: 3091–4179 respectively) showed significantly greater migration towards eotaxin than healthy controls (median: 2304, IQR: 1519–2723. p=0.0238, p=0.038 respectively) (figure 1). Conclusion: Eosinophils in COPD show enhanced migration towards IL-5 and eotaxin. Whether this is a mechanism underlying T2 high COPD requires further investigation.