Antibodies are molecules produced by a human’s immune system to counteract bacteria and viruses. When a bacterial or viral pathogenic molecule (a so-called antigen) is detected, an antibody neutralizes it by binding to it. However, autoantibodies are sometimes produced against our own protein and cause autoimmune diseases. For the autoantibody known as ANCA (antineutrophil cytoplasmic antibody) cause ANCA-associated vasculitis (AAV), at least two antigens exist: proteinase 3 and myeloperoxidase (abbreviated as PR3 and MPO, respectively).
