Mapping of eosinophil and basophils in COPD lung tissues

Rationale: Although COPD is regarded as a non-eosinophilic and Th2-low disease, a significant proportion of the patients display elevated blood and sputum eosinophils. The nature of the eosinophilia in COPD and presence of basophils in lung tissues remains unexplored. Objectives: This study maps eosinophil and basophil tissue infiltration and associated Th2 immunity in major lung compartments across COPD severities. Methods: Eosinophils, basophils and GATA3+ cells were investigated in lung tissues and lymph nodes obtained from 30 COPD patients divided into GOLD I, II-III, and IV categories. Never-smoking and smoking non-COPD subjects (n=15) served as controls. Bronchi, bronchioles, pulmonary vessels, alveolar regions, and lymph nodes from > 140 tissue blocks underwent automated immunohistochemical staining and quantitative image analysis. Results: In COPD, the overall tissue density of eosinophils and basophils were increased (p 0.0001) and co-localization studies revealed a strong regional spatial relationship between eosinophils, basophils as well as GATA3+ cells. Conclusions: This study reveals that a surprisingly large proportion of COPD patients have focal lung infiltrations of eosinophils and basophils, which are likely caused by highly regionalized and still unexplored Th2 responses.