Human Myeloperoxidase Assay Kit

Background

Human myeloperoxidase (MPO) is a hemoprotein composed of two heme-containing heavy subunits of 53 kDa and of two light subunits of 15 kDa.  MPO is stored in the granules of neutrophils and monocytes, and is released in response to leukocyte activation.  MPO acts as a catalyst in the production of hypochlorous acid (HOCl), a powerful oxidant produced from chloride ion (Cl-) and hydrogen peroxide (H2O2).  Although MPO is important to the immune system, it also plays a role in several inflammatory conditions.

Elevated MPO levels have been linked to coronary artery diseases.  High concentrations of MPO and its oxidation products are found in areas of plaque deposits present in atherosclerosis.  MPO also affects cholesterol levels through the oxidation of LDL and HDL.

As a specific marker for polymorphonuclear cells (PMNs), MPO is released extracellularly via degranulation after PMN activation. Thus, extracellular MPO is an index of PMN activation in inflammatory processes that lead to disease pathology, such as cardiovascular disease.  Elevated levels of MPO present in serum and plasma indicate a greater risk of myocardial injury and unstable plaque formations.  Therefore, MPO levels can be used to predict potentially negative cardiac events.

Antibodies to MPO are present in human plasma, and have been characterized as part of the anti-neutrophil cytoplasmic antibodies (ANCA) set of autoantibodies.

Principles of Procedure

The Human MPO EIA Kit is a sandwich ELISA (Enzyme-Linked Immunosorbent Assay) that measures MPO in plasma/serum samples. The MPO in the sample interacts with and binds to the anti–MPO antibody coated on the wells. The plate is then washed to remove all unbound materials and anti–MPO, conjugated with HRP (horseradish peroxidase), is added to the plate wells. The HRP conjugate binds to the MPO that is bound to the anti–MPO of the plate. After washing the plate again, TMB is added, which will produce a blue hue. A darker blue color corresponds to a higher concentration of MPO. After reaction has occurred with the conjugate a stop solution is added, producing a yellow hue. The absorbance is measured at 450 nm.

Typical Standard Curve

References

1.    Klebanoff, S. J.; (2005) J of Leuk. Bio. 77:598
2.    Klein, J.; (1982) Immunology The Science of Self-Nonself Discrimination p 427
3.    Renliang, Z., et al.; (2001) JAMA 286(17):2136, 2140
4.    Reumaux, D., et al.; (2003) J of Leuk. Bio. 73:846
5.    Van der Woode, F.J., and Schmitt, W.H.; (2004) Clinical Applications of Anti-neutrophil Cytoplasmic Antibody Testing. http://www.medscape.com/viewarticle/467031. Accessed July 31, 2008