Increased CD69 expression on activated eosinophils in eosinophilic chronic rhinosinusitis correlates with clinical findings

Abstract Background Eosinophilic chronic rhinosinusitis (ECRS) is a subtype of chronic rhinosinusitis associated with asthma. CD69 is an important marker of activation for eosinophils. But, whether a correlation exist between the CD69 expression on eosinophils and clinical findings is unclear. Methods We performed quantitative PCR and/or flow cytometry using tissue and purified eosinophils from the blood and nasal polyps of 12 patients with ECRS and from 8 patients without ECRS (controls). We assessed clinical findings including nasal polyp (NP) scores, sinus CT findings, and pulmonary function test results, and examined their possible association with the CD69 expression. We also performed CD69 cross-linking experiments in mouse eosinophils to investigate the functional role of CD69. Results Levels of cytokine mRNAs (IL-4, -5, -10, and -13) were significantly higher in purified NP eosinophils and tissues from patients with ECRS than the levels of those in controls. The expressions of major basic protein (MBP), eosinophilic cationic protein (ECP), eosinophilic-derived neurotoxin (EDN), eosinophil peroxidase (EPX) in cytotoxic granules, and CD69 mRNA were significantly higher in purified eosinophils from NPs than in those from blood. We also found a correlation between expression of CD69 and clinical findings. Moreover, we found EPX release from mouse eosinophils following CD69 cross-linking. Conclusions These data suggest that increased CD69 expression by eosinophils is not only a biomarker for nasal obstruction and pulmonary dysfunction, but also a potential therapeutic target for patients with ECRS and asthma.