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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 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 pANCA sera has been identified as myeloperoxidase.

The existence of autoantibodies to bactericidal/permeability-increasing protein (BPI) was first described when it was noticed that 11 of 51 sera that were cANCA positive in immunofluorescence, recognised a 57 kDa antimicrobial cationic protein known as CAP57 in both ELISA and Western blot.  It is now known that CAP57 and BPI are identical.

Autoantibodies directed to negatively charged phospholipids, in particular cardiolipin, have been detected in the serum of patients with systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS). APS is characterised by venous and arterial thrombosis, recurrent spontaneous abortions and thrombocytopenia. It is now known that a serum cofactor, β₂-glycoprotein 1, is required for the binding of cardiolipin by autoantibodies in the sera of patients with APS. By contrast, anticardiolipin antibodies from patients with infectious diseases (in particular, syphilis) do not require this cofactor.

AROTEC`s Rheumatoid Factor (RF) antigen (Human IgG Fc fragment) is purified from human plasma and can be used to detect rheumatoid factors in patient sera. Rheumatoid factors are a subcategory of immunoglobulins that specifically bind to the Fc regions of IgG. Elevated concentrations of rheumatoid factors are often correlated with a more severe course of the disease. IgM RF may precede the onset of RA by several years. In established RA, high titer serum IgM RF indicate poor prognosis.