MPO and microscopic polyangiitis: myeloperoxidase-ANCA2 in most patients with MPA are positive which can be mainly evoked by the ANCA-mediated over-activation of neutrophils and release of inflammatory cytokines, reactive oxygen species and plasmin.[4] The excessive activation of neutrophils by ANCA could result in the formation of Neutrophil extracellular traps, which are involved not only in ANCA-mediated vascular injury but also in the production of ANCA itself.[5]