Proteinase-3 is present within primary azurophil granules of neutrophils (PMNs) and lysozymes of monocytes. PR3 translocates to the cell surface, where PR3-ANCAs can interact with their antigens and activate PMNs.
PR3 encodes proteinase-3 that is the target of antineutrophil cytoplasmatic autoantibodies (ANCAs) observed in patients sera with Wegener granulomatosis.