Myeloperoxidase AssayNotes

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Myeloperoxidase (MPO) is a hemoprotein that is abundantly expressed in polymorphonuclear leukocytes (neutrophils) and secreted during their activation. The presence of a peroxidase in the cytoplasmic granules of leukocytes was suggested at the beginning of 20th century but it was the early 1940s that it was purified for the first time. Native MPO is a covalently bound tetrameric complex of two glycosylated alpha chains (MW 59 – 64 kDa) and two unglycosylated beta chains (MW 14 kDa) with total MW about 150 kDa and theoretical pI 9.2 (1).

MPO plays an important role in neutrophil microbicidal action through catalyzing chloride ion oxidation to hypochlorous acid, which is a potent antimicrobial agent. On the other hand, it was demonstrated that MPO causes oxidative modification of low density lipoprotein (LDL) to a high uptake form that is considered to be a key event in the promotion of atherogenesis (2). That’s why MPO is believed to participate in the initiation and progression of cardiovascular diseases. MPO possesses potent proinflammatory properties and may contribute directly to tissue injury. In addition, MPO is shown to be involved in pathogenesis of lung cancer (3), Alzheimer’s disease (4) and multiple sclerosis (5).

Now MPO is believed to be one of the most promising cardiac markers. Recently it was demonstrated that an increased MPO level in patient’s blood serves as a risk marker for atherosclerosis (6) and coronary artery disease (7). It predicts the early risk of myocardial infarction, as well as the risk of other major adverse cardiac events in patients with chest pain in the ensuing 30-day and 6-month periods (8, 9). The value of MPO as a marker is in that MPO predicts these outcomes independently of other known laboratory tested risk factors, including troponins, creatine kinase MB isoform (CK-MB), C-reactive protein (CRP) and lipid profile. Moreover, unlike troponins I and T, CK-MB, and CRP, MPO makes it possible to identify patients at risk for cardiac events in the absence of myocardial necrosis (8). All these factors make MPO measurements in patients an indispensable procedure to reveal patients with chest pain that are at increased risk of cardiovascular complications.

There are some autoimmune diseases connected with development of autoanibodies against MPO. MPO is a main target of anti-neutrophil cytoplasm antibodies (ANCA) – serological markers for certain systemic vasculitides, e.g. periarteriitis nodosa, microscopic polyarteriitis and pulmonary eosinophilic granulomatosis (Churg-Strauss syndrome) (10). Low to moderate anti-MPO autoantibody levels are also reported in rheumatoid arthritis.

Our suppliers have been producing human MPO for many years. Today it is our pleasure to announce that new generation of anti-MPO monoclonal antibodies suitable for the development of quantitative MPO immunoassay is available from Advanced ImmunoChemical. Sandwich immunoassays utilizing these antibodies demonstrated great results in precise MPO immunodetection in patient’s blood samples.

Research Courtesy of HyTest

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