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Beckman Coulter OSR61173 Specific M Protein Immunoglobulin M (IgM)


Brand: Beckman Coulter
Manufacturer SKU: OSR61173
Analyzer Type: Chemistry Analyzer
Test Type: Antibody Test
Test Name: Immunoglobulin M (IgM)
SKU: OSR61173 Category:


Beckman Coulter OSR61173 Immunoglobulin M (IgM) / m protein immunoglobulin protein:

IgM is a particularly avid class of antibody, being a pentamer of five m protein IgG equivalents, with 10 Fab fragments and therefore 10 antigen-binding sites. Because IgM is formed early in the immune response and is later replaced by m protein IgG, specific antibodies of the IgM class are diagnostic of recent (or chronic) infection. IgM is the first immunoglobulin found in the fetus as it develops immunological competency in the second half of pregnancy. Since IgM does not cross the placenta from mother to fetus, the presence of IgM antibodies against a particular virus in a newborn is indicative of intrauterine viral infection.

General Characteristics of Immunoglobulin Molecules

Beckman Coulter OSR61173 Immunoglobulin M (IgM) is a high molecular weight m protein immunoglobulin protein (macroglobulin), consisting of five or rarely of six subunits (IgM monomers). Like m protein IgG molecules, the IgM monomers are composed of two heavy and two light chains, which are linked together by disulfide bridges. The IgM monomers are found at a low concentration in human serum. Each pentameric IgM molecule is composed of 10 heavy (μ) chains, 10 light chains and usually one joining (J) chain (Metzger, 1970).

The B cells can also secrete functionally active IgM hexamers lacking J chains but the amount of hexamers in serum is no more than 5% of total IgM (Brewer et al., 1994). The carbohydrate content of IgM is high, about 12%. A pentameric IgM molecule has 10-antigen combining sites and can bind 10 small antigens (haptens).

However, due to steric restrictions, only five large antigen molecules can be bound by one IgM molecule. The antibody activity of IgM is destroyed upon reduction of the intersubunit disulfide linkages. Such a reduction can easily be achieved with very low concentrations of reducing agents, such as dithiothreitol or mercaptoethanol.