Highly Purified (~95%). Proteinase 3 also known as PRTN3 is an enzyme expressed mainly in neutrophil granulocytes. Its exact role in the function of the neutrophil is unknown but in human neutrophils proteinase 3 contributes to the proteolytic generation of antimicrobial peptides. It is also the epitope of anti-neutrophil cytoplasmic antibodies (ANCAs) of the c-ANCA (cytoplasmic subtype) class, a type of antibody frequently found in the disease Wegener's granulomatosis. Anti-neutrophil cytoplasmic antibodies (ANCAs) are autoantibodies produced in response to neutrophil cytoplasmic enzymes, and evaluating the levels of ANCAs is useful for making a diagnosis of systemic vasculitis such as granulomatosis with polyangiitis (Wegener's) (GPA) or microscopic polyarteritis (MPA). The majority of p-ANCAs and c-ANCAs have been proven to be equivalent to MPO- and PR3- ANCAs, respectively. Patients with MPA and Churg- Strauss syndrome are positive for p-ANCA, and those with GPA are positive for c-