Saint John on Patmos: Revelations of the Role of Antineutrophil Cytoplasmic Antibody (ANCA) in Vasculitis.

Diagnosis of vasculitis is based on the presence of histologic features and serological testing for antineutrophil cytoplasmic antibodies (ANCA). In patients with vasculitis, two types of ANCA have been identified: ANCA directed against the neutrophil serine protease proteinase-3 (PR3) which results in a cytoplasmic immunofluorescence pattern (c-ANCA) and ANCA directed against the neutrophil enzyme myeloperoxidase (MPO), which results in a perinuclear immunofluorescence pattern (p-ANCA). Question is if the presence of ANCA is the consequence of abnormal neutrophil adhesion, activation, and apoptosis. Or is it, through mechanisms which are not totally clear for the moment, the cause of vasculitis. In the latter case it has to be postulated that ANCA autoantigens are expressed on the cell surface of viable, or activated, or early-apoptotic neutrophils.