Sphingosine-1-phosphate (S1P) receptor antagonist inhibited C5a-primed neutrophils for antineutrophil cytoplasmic antibody (ANCA)-induced respiratory burst and degranulation. (A) Neutrophils were incubated with different concentrations of FTY720, and the mean fluorescence intensity (MFI) value for dihydrorhodamine (DHR) oxidation decreased, compared with C5a-primed neutrophils for ANCA-induced activation. Cells were incubated with FTY720 at different concentrations and times (10nM, 5 minutes; 10nM, 15 minutes; 50nM, 15 minutes; respectively). (B) Neutrophil respiratory burst induced by patient-derived myeloperoxidase (MPO)-ANCA-positive IgG or proteinase-3 (PR3)-ANCA-positive IgG was measured by conversion of DHR-123 to rhodamine-123 in C5a-primed cells. Inhibition of S1P reduced C5a-primed neutrophils for ANCA-induced respiratory burst. (C) ANCA-induced neutrophil degranulation was determined by measuring the lactoferrin concentrations in the supernatant of neutrophil degranulation reaction. Inhibition of S1P reduced ANCA-induced lactoferrin release. Bars represent mean ± SD of repeated measurements of neutrophils from five independent experiments and donors.