Membrane PR3-positive and NB1-positive neutrophils are identical. Neutrophils were stained with anti-PR3 and PE-labeled secondary antibody (x-axis) and FITC-labeled antibodies against NB1, CD16b, and CD66b (A). Measurements were taken after the appropriate compensation. Percentages of cells in the quadrants are noted. (B) Neutrophil membrane PR3-positive and -negative subpopulations were separated by magnetic cell sorting and stained with directly labeled anti-NB1 antibody. mPR3-negative cells do not stain for NB1 (bold line), whereas mPR3-positively sorted cells are recognized by the anti-NB1 antibody (dotted line).