Antineutrophil antibodies (c-ANCA, p-ANCA, a-ANCA)

General Information

ANCA antibodies were first described in 1982 in patients with autoimmune glomerulonephritis.

ANCA are antibodies (IgG type, less often IgA and IgM) directed mainly against antigens from the cytoplasm of neutrophil granulocytes (molecular targets are enzymes from the primary or azophilic granules of neutrophil granulocytes) and monocytes.

Using ethanol-fixed neutrophils as a substrate, 3 main patterns have been described in indirect immunofluorescence studies:

• Cytoplasmic (c-ANCA) , characterized by diffuse cytoplasmic granular fluorescence, with a central interlobular focus; the antigen is present Proteinase 3-with (PR3) , a component of both azorophil granules of myeloid cells and monocyte lysosomes;
• Perinuclear (p-ANCA) , characterized by homogeneous perinuclear (ring) fluorescence, without cytoplasmic fluorescence; the main antigen is Myeloperoxidase (MPO) , a neutrophil granulation protein that is involved in metabolic processes, such as the generation of oxygen radicals. This pattern occurs due to the migration of positively charged (cationic) antigens, when ethanol is used, towards the negatively charged nuclear envelope. When formalin is used instead of ethanol to fix neutrophils, the target antigen is immobilized and cytoplasmic fluorescence is obtained.
• Atypical ANCA (x-ANCA) Antineutrophil cytoplasmic antibodies are a type of antineutrophil antibody that is directed against antigens located near the nucleus of neutrophils. They are often used in the diagnostics of vasculitis and some autoimmune diseases.