MPO and vasculitis: It is important to note that the majority of work demonstrating a proinflammatory T cell response to MPO has been performed in patients with anti-MPO glomerulonephritis and vasculitis, who present with ANCA (antineutrophil cytoplasmic antibodies) which react to proteinase 3 and MPO in particular; this disease may involve unusual mechanisms of action of MPO not found in healthy individuals including it acting as an autoantigen.