The role of low density granulocytes and NETosis in the pathogenesis of adult-onset Still's Disease.

OBJECTIVES: To analyse the potential contribution of low-density granulocytes (LDGs) and NETosis, as well as the differential protein cargo of neutrophil extracellular traps (NETs), as physiopathogenic mechanisms of adult-onset Still's disease (AOSD). METHODS: We recruited 30 patients with AOSD according to the Yamaguchi diagnostic criteria. LDGs were addressed by multiparametric flow cytometry as those CD14-, CD15+, CD10+ cells in the peripheral blood mononuclear cells fraction. NETs were quantified by ELISA, immunofluorescence and fluorescence spectrometry. The expression of LL-37 and high mobility group box 1 (HMGB-1) in NETs was measured by immunofluorescence and confocal microscopy. Additionally, normal density neutrophils from healthy controls were stimulated with serum from patients with AOSD and NET induction was assessed by immunofluorescence. RESULTS: Patients with active disease as well as those with arthritis, cutaneous manifestations and fever had a higher amount of NETs and LDGs. Serum NETs from AOSD patients correlated with the number of swollen joints (r=0.41, p=0.032), absolute number of monocytes (r=0.529, p=0.005). The spontaneous NETs from patients with cutaneous manifestations and fever had higher cargo of HMGB-1 compared with patients in remission. CONCLUSIONS: LDGs and NETs are increased in patients with active AOSD and correlate with particular clinical features. Patients with cutaneous lesions and fever present a higher cargo of HMGB1 in their spontaneous NETs.