Myeloid and Histiocytic Markers. The myeloperoxidase antibody reacts with the myeloperoxidase enzyme found in granules of early and late myeloid precursors, as well as mature neutrophils. It is very specific for myeloid proliferations.

Abbreviated MPO. An enzyme found in many tissues and cells throughout the body. For reasons that are unknown, many patients with Wegener's granulomatosis and microscopic polyangiitis make antibodies to this protein.

Myeloperoxidase (MPO) is a peroxidase enzyme most abundantly present in neutrophil granulocytes (a subtype of white blood cells). It is a lysosomal protein stored in azurophilic granules of the neutrophil. MPO has a heme pigment, which causes its green color in secretions rich in neutrophils, such as pus and some forms of mucus.