Enhanced release of neutrophil extracellular traps from peripheral blood neutrophils in patients with rheumatoid arthritis

Background/objectives Neutrophils are the most abundant cell type identified in joints from patients with rheumatoid arthritis (RA), with a key role in inflammation and cartilage damage. Activated neutrophils may form extracellular traps (NETs), with potent pro-inflammatory and immunostimulatory activity. The authors sought to assess the role of NET release in RA pathogenesis. Materials/methods Peripheral blood neutrophils from RA patients (n=3) (DAS28>5.1) and control subjects (n=7) were isolated. NET formation from RA neutrophils and control neutrophils treated with RA serum (n=7) or synovial fluid (n=2) was assessed by immunofluoresence microscopy, using co-staining with myeloperoxidase and DAPI. The percentage of NET releasing cells was determined by examining 200 cells per sample in a double blind fashion. Time course experiments revealed optimal NET release at 3 h. Results Freshly isolated RA neutrophils underwent spontaneous NET release at higher rates compared to normal controls (11.67±2.1% vs 3.21±0.9%, p