Hydrogen peroxide production (mean of fluorescence intensity; arbitrary units) in primed human peripheral-blood neutrophils before (gray curve) and after (black curve) stimulation with IVIg assessed by flow cytometry measuring the oxidation of dihydrorhodamine 123 to rhodamine 123 (x-axis; arbitrary units). (A) Oxidative burst induced by batch B1 (IgG ANCA 1:32, mean 1.72). (B) Oxidative burst induced by IVIg A1 (IgG ANCA 1:1024, mean 4.96). Incubation time 100 minutes, IVIg concentration 2.5 mg/mL in both experiments. Cells were prestimulated with TNFα (1 ng/mL) for 15 minutes.