Serum protein electrophoresis

Serum protein electrophoresis is a laboratory test that examines specific proteins in the bloodcalled globulins. Blood must first be collected, usually into an airtight vial or syringe. Electrophoresis is a laboratory technique where the blood serum (the fluid portion of the blood after the blood has clot) is placed on special paper treated with agarose gel and exposed to an electric currentto separate the serum protein components into five classifications by size and electrical charge, those being albumin, alpha-1-globulins, alpha-2-globulins, beta globulins, and gamma globulins.

Albumin

A fall of 30% is necessary before the decrease shows on electrophoresis. Usually a single band is seen. Heterozygousindividuals may produce bisalbuminaemia - two equally staining bands, the product of two genes. Some varients give rise to a wide band or two bands of unequal intensity but none of these varients is associated with disease. Increased mobility results from the binding of bilirubin, nonesterified fatty acids, penecillinand acetyl salicyclic acid, and occaisionally from tryptic digestion in acute pancreatitis.

Absence of albumin is rare. This condition is called analbuminaemia. A decreased level of albumin, however, is common in many diseases and is especially important in liver disease.

Albumin - Alpha-1 Interzone

Even staining in this zone is due to alpha-1 lipoprotein (High density lipoprotein- HDL). Decrease occurs in severe inflammation, acute hepatitis, and cirrhosis. It is not easy to recognise.

An increse appears in severe alcoholics and in women during pregnancy and in puberty.

The high levels of AFP that may occur in hepatomasmay result in a sharp band between the albumin and the alpha-1 zone.

Alpha-1 Zone

Orosmucoidand antitrypsinmigrate together but orosmucoid stains poorly so alpha-1 antitrypsin constitutes most of the alpha-1 band. Alpha-1 antitrypsin has an SG group and thiol compounds may be bound to the protein altering their mobility. A decreased band is seen in the deficiency state. It is decreased in the nephrotic syndrome.

Bence Jones proteinmay bind to and retard the alpha-1 band.

Alpha-1 - Alpha-2 Interzone

Two faint bands may be seen representing alpha-1 antichymotrypsin and vitamin Dbinding protein. These bands fuse and intensify in early inflammation due to an increase in alpha-1 antichymotrypsin, an acute phase protein.

Alpha-2 Zone

This zone consists principally of alpha-2 macroglobulin and hepatoglobulin. There are typically low levels in haemolytic anaemia(hepatoglobulin is a suicide molecule which binds with free haemoglobinreleased from red blood cellsand these complexes are rapidly removed by phagocytes). Hepatoglobulin is raised as part of the acute phase response and therfore there is a typical increase in alpha-2 inflammation. A normal alpha-2 and a raised alpha-1 is typical in hepatic metastasesand cirrhosis.

Hepatoglobulin/haemaglobin complexes migrate more cathodally than hepatoglobulin as seen in the alpha-2 - beta interzone. This is typically seen as a broadening of the alpha-2 zone.

Alpha-2 macroglobulin is raised in children and the elderly. This is seen as a sharp front to the alpha-2 band. It is of little diagnostic significance but is markedly raised in association with glomerilar protein loss - the characteristic increased alpha-2 of the nephrotic syndrome, associated with decreased albumin.

Alpha-2 globulins can be raised in cirrhosis, diabetes, and malignancy.

Alpha-2 - Beta Interzone

Cold insoluble globulin forms a band here which is not seen in plasma because it is precipitated by heparin. There are low levels in inflammation and high levels in pregnancy.

B lipoprotein forms an irregular crenatedband in this zone. High levels are seen in type II hypercholesterolaemiaand in the nephrotic syndrome.

Beta Zone

Transferrincomprises the beta-1 band. Increased beta-1 protein is typical of iron deficient anaemia, pregnancy, and oestrogentherapy.

Beta-2 is comprised of C3 (Compliment protein3). It is raised in the acute phase response.

Gamma Zone

The immunoglobulinsare the only proteins present in the normal gamma region. IgAhas the most anodal mobility and migrates in the beta-gamma region. High levels give rise to beta/gamma fusion as in cirrhosis, respiratory infection, skin disease, or rheumatiod arthritis. IgA deficiency occurs in 1:500 of the population, as is suggested by a pallor in the gamma zone.

Commonest causes of hypergammaglobulinaemia detected by electrophoresis are severe infection, chronic liver disease, systemic lupus erythematosus, and rheumatoid arthritis.

Hypogammaglobulinaemia is easily identifiable. It is normal in infants.

Zones or faint bands in the gamma region are often seen as a result of clones of immunoglobulins responding to antigenic challenge, e.g. in chronic hepatitisand chronic viral infections.

C reactive proteincan be seen as a faint band when the level is grossly abnormal, e.g. in tissuedamage.

Dense narrow bands composing of immunoglobulins of a single class and containing only one type of light chainare known as paraproteinsor M (monoclonal) proteins. IgA paraproteins migrate most anodally and may be confused with beta globulins. Paraproteins can arise from benign or malignant clones of B cellsand their recognition and investigation is very important.

Lysozymemay be seen as a band cathodal to the slowest gamma in myelomonocytic leukaemiain which it is released from tumourcells.

Myelomais the commonest cause of IgA and IgGparaproteinaemias but chronic lymphatic leukaemia and lymphosarcomaare not uncommon and usually give rise to IgMparaproteins. Waldenstrom's macroglobulinaemia, a malignant lymphoma, also gives rise to an IgM paraprotein.

Benign paraproteins are usually faint and do not show immunoparesis. Faint bands seen in the gamma region may be due to light chain disease, particularly if there is immune peresis.

Fibrinogenfrom plasmasamples will be seen in the fast gamma region.

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It uses material from the http://en.wikipedia.org/wiki/Serum+protein+electrophoresis Wikipedia article Serum protein electrophoresis.