Perinuclear antineutrophil cytoplasmic antibodies

p-ANCA, or MPO-ANCA, or Perinuclear Anti-Neutrophil Cytoplasmic Antibodies, are antibodies that stain the material around the nucleus of a neutrophil. They are a special class of Anti-Neutrophil Cytoplasmic Antibodies.

This pattern occurs because the vast majority of the antigens targeted by ANCAs are highly cationic (Positively charged) at pH 7.00. During ethanol (pH ~7.0 in water) fixation, antigens which are more cationic migrate and localize around the nucleus, attracted by its negatively charged DNA content. Antibody staining therefore results in fluorescence of the region around the nucleus.

p-ANCAs stain the perinuclear region by binding to specific targets. By far the most common p-ANCA target is myeloperoxidase (MPO), a neutrophil granule protein whose primary role in normal metabolic processes is generation of oxygen radicals.

ANCA will less commonly form against alternative antigens that may also result in a p-ANCA pattern. These include lactoferrin; elastase; and cathepsin G.

When the condition is a vasculitis, the target is usually MPO. However, the proportion of p-ANCA sera with anti-MPO antibodies has been reported to be as low as 12%.

p-ANCA is associated with several medical conditions:

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