Anti-neutrophil cytoplasmic antibody (ANCA): perinuclear ANCA (MPO), cytoplasmic ANCA (PR3)
Chemiluminescent Immunoassay (CIA)
Semi-Quantitative • Negative <20 CU • Positive ≥20 CU
Mitogen’s ANCA/PR3, MPO assay is an autoimmune diagnostic test that detects autoantibodies to ANCA/PR3 and MPO. Sera are tested for anti-MPO and anti-PR3 by a chemiluminescence assay (CIA) which is an essential test when conventional ANCA testing is negative. The CIA has advantages of higher sensitivity and specificity for these ANCA-related vasculitis targets.
MPO (Myeloperoxidase) is a peroxidase enzyme that is most abundantly expressed in neutrophil granulocytes (a subtype of white blood cells). The antimicrobial activity of MPO results in the production of hypohalous acids from hydrogen peroxide. It is a lysosomal protein stored in azurophilic granules of the neutrophil and released into the extracellular space during degranulation. Another key function of MPO is the oxidation of apoA-I which reduces HDL-mediated inhibition of apoptosis and inflammation.
PR3 (Proteinase 3 or PRTN3) is a serine protease enzyme expressed mainly in neutrophil granulocytes. Its exact role in the function of the neutrophil is unknown, but, in human neutrophils, PR3 contributes to the proteolytic generation of antimicrobial peptides. It is also the target of anti-neutrophil cytoplasmic antibodies (ANCAs) of the c-ANCA (cytoplasmic subtype) class, a type of antibody frequently found in the disease granulomatosis with polyangiitis.
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