Eosinophil Biology in COPD

Chronic obstructive pulmonary disease (COPD) is a lethal disease that is predicted to become the third leading cause of death globally within 3 years.1 Recent research has highlighted the heterogeneity of the pathologic characteristics of COPD, indicating that disease mechanisms are complex. Inflammatory pathways implicating neutrophils have been emphasized,2 but attention has recently focused on the persistent blood and airway eosinophilia that is found in up to 40% of patients with COPD, even in the absence of a history of asthma; such patients have a higher risk of exacerbations than patients without eosinophilia.3,4 Guidelines have generally recommended a “one size . . .