• Joanna Natorska, Michał Ząbczyk, Jakub Siudut, Piotr Krawiec, Lucyna Mastalerz, and Anetta Undas.
• Institute of Cardiology, Jagiellonian University Medical College, Kraków; and John Paul II Hospital, Kraków, Poland. j.natorska@szpitaljp2.krakow.pl.
• Clin Exp Rheumatol. 2017 Mar 1; 35 Suppl 103 (1): 27-32.

ObjectivesEosinophilic granulomatosis with polyangiitis (EGPA) is associated with an inflammation and the presence of antineutrophil cytoplasmic antibodies (ANCA). Thus, we investigated the impact of ANCAs and eosinophilic inflammation on neutrophil activation and extracellular traps (NETs) formation.MethodsWe recruited 29 patients in the remission of EGPA (17 ANCA-negative and 12 ANCA-positive, including 7 p-ANCA-positive and 5 c-ANCA-positive patients). Healthy donors' neutrophils were stimulated with EGPA patients' serum. NETs formation was assessed by immunofluorescence and scanning electron microscopy.ResultsEGPA patients presented enhanced ability to generate NETs compared to healthy subjects (20.3±8.2% vs. 2.7±1.5%, p=0.0036). However, there were no differences in NETs formation between ANCA-positive and ANCA-negative patients (23±11.2% vs. 17±6.1%, p=0.15). There was also no correlation between NETs generation and the amount of circulating DNA in EGPA patients. Among ANCA-positive patients, p-ANCA-positives showed the highest percentage of NETs as compared to cANCA-positive and ANCA-negative patients (27.3±10.3% vs. 17.8±10.5% and vs. 17±6.1%, both p<0.01, respectively). Eosinophils number correlated with the percentage of NETs in the whole EGPA group (r=0.53, p=0.039), but we failed to observe the correlation with an eosinophil cationic protein (r=0.49, p=0.058).ConclusionsEGPA patients' serum has the ability to induce NETosis with no regard to the ANCA status in contrast to other vasculitides, where p-ANCA were considered as the main factor. Interestingly, NETs formation in EGPA patients connected with the number of eosinophils might be of major relevance. Further studies are required to assess which eosinophil-derived factors might be responsible for the neutrophils activation in EGPA patients.

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