Native - Human Neutrophils
Autoantibodies staining the nuclei or the perinuclear zone of neutrophils by indirect immunofluorescence are referred to as pANCA whereas those giving a clear cytoplasmic fluorescence are referred to as cANCA. The antigen recognised by most cANCA sera has been identified as proteinase 3 (also known as myeloblastin, p29 or AGP7).
Autoantibodies to proteinase 3 are found in the sera of patients with active Wegener's granulomatosis and less often in other types of systemic vasculitis including microscopic polyangiitis, idiopathic crescentic glomerulonephritis, Churg-Strauss syndrome and polyarteritis nodosa.
Proteinase 3 (PR3) is a serine proteinase with proteolytic activity towards a range of substrates. The protein has been described as having antibiotic and growth-promoting properties but has been noted to causing emphysema when administered by tracheal insufflation.
Proteinase 3 cDNA has been cloned and sequenced, revealing the protein to be a basic 25 kDa glycoprotein of 228 amino acids. The protein reveals a triplet of bands in the range 29-32 kDa when subjected to denaturing SDS-electrophoresis, probably caused by differing degrees of glycosylation. Although proteinase 3 shows significant homology to elastase and cathepsin G, cANCA sera do not cross react with these serine proteases.
Autoantibodies to PR3 appear to recognise conformational epitopes and have been reported to interfere with inactivation of the enzyme by α1-antitrypsin and to also inhibit proteolytic activity itself.
Proteinase 3 (cANCA) datasheet
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