Membrane PR3 expression highly correlates with membrane expression of granulocyte antigen NB1. Live neutrophils were surface stained with monoclonal antibodies. Fluorescence was measured by flow cytometry. Percentages of membrane PR3- and NB1-positive cells were identical in donors with different percentages of membrane-positive cells (A-B, 90%;C, 0%). MFI of both proteins increased after stimulation with TNF-α (A; bold line for cells stimulated with buffer control and dotted line for TNF-α stimulation) with fMLP (bold line for buffer control, dashed line for 10−6 M fMLP). In contrast, the NB1- and PR3-positive percentage remained unchanged, and no increase in the expression of either molecule occurred with TNF-α when cells from an mPR3/NB1-negative donor were used (C). (D) The correlation is shown of PR3 and NB1 percentages in 51 healthy donors (r = 0.996, P < .001). (E) The values are given for patients with ANCA-associated vasculitis (r = 0.999, P < .001).
