Abstract Background Eosinophilic Granulomatosis with Polyangiitis (EGPA) is a rare autoimmune disease characterized by asthma-like symptoms, eosinophilia, and vasculitis. Its pathogenesis is not fully understood, but abnormal activation of eosinophils has been considered a key factor, and eosinophil extracellular traps (EETs) may play an important role in tissue damage and inflammation in EGPA. Methods We used ELISA to measure ECP-DNA levels in serum and induced sputum from healthy controls (HC), severe eosinophilic asthma (SEA) patients, active-phase EGPA (aEGPA) patients, and remission-phase EGPA (rEGPA) patients. Immunofluorescence with citH3 and ECP antibodies was used to detect EETs expression in bronchial mucosa. Inclusion criteria for the HC group were age 18-65 years, no history of smoking or secondhand smoke exposure, and no chronic or autoimmune diseases. The SEA group was diagnosed according to the 2023 GINA guidelines, while the aEGPA and rEGPA groups were diagnosed based on the 2017 MIRRA criteria, with disease activity assessed according to the 2021 ACR guidelines. Results Both the SEA and aEGPA groups showed significantly higher eosinophil levels compared to the HC group, indicating an association with eosinophilia. Elevated levels of dsDNA and ECP-DNA were observed in the peripheral blood and induced sputum of the SEA and aEGPA groups, with intermediate levels in the rEGPA group. The aEGPA group exhibited significant eosinophil infiltration and extensive EETs formation in bronchial mucosa. In contrast, the SEA group showed eosinophil infiltration without prominent EETs formation, while the rEGPA group had reduced eosinophil infiltration and minimal EETs expression. Conclusion Our findings demonstrate that EETs play a pivotal role in the pathogenesis of active-phase EGPA. The marked increase in dsDNA and ECP-DNA levels, combined with extensive eosinophil infiltration and robust EETs formation in aEGPA patients, distinguishes them from SEA and rEGPA cases. These results suggest that EETs and their associated biomarkers may serve as reliable indicators of disease activity and potential therapeutic targets for EGPA. This abstract is funded by: no
Q Zhang (Fri,) studied this question.