High serum IFNα levels in anti-neutrophil cytoplasmic antibody-associated vasculitis patients. (A) Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) sera contained higher levels of interferon alpha (IFNα) than the healthy control (HC) sera (U = 1,438.00, ***P = 0.000). (B) AAV patients with crescentic glomerulonephritis (GN) showed higher levels of IFNα as compared with the noncrescentic GN AAV patients (***P <0.001) and the HCs (***P <0.001). Serum levels of IFNα in the patients without crescentic GN were also significantly higher than those in the HCs (#P < 0.05). (C) Patients with high IFNα expression (>958.5 pg/ml) had a greater risk of having crescentic GN than patients with low IFNα expression (<958.5 pg/ml) (χ2 = 16.835, P = 0.000).