Immunoglobuline Quantitative A, G, M, E

What is it: This test quantifies Immunoglobulin A; immunoglobulin E; immunoglobulin G; and immunoglobulin M.

Functions:

IgM Total Antibodies

What is it: Immunoglobulin M is the largest antibody in the blood and the primary antibody against A and B on the red blood cell.

Function: IgM appears at the onset of infection and sometimes after another exposure. They do not cross the placenta.For these reasons the demonstration of IgM-specific antibody is useful in assessing whether a particular infection is acute (in which case IgM antibodies will be present) or chronic (IgG antibodies will predominate) and whether a newborn has a congenital infection (a newborn with IgM antibody is infected; a newborn with IgG antibody has passively acquired maternal antibody, which simply crossed the placenta). It is the antibody type produced initially in the immune response and the first immunoglobulin class to be synthesized by a fetus or newborn.

Tested for: Quantitation of IgM is used to evaluate humoral immunity; establish the diagnosis and monitor therapy in macroglobulinemia of Waldenstrm, and plasma cell myeloma. IgM levels are used to evaluate likelihood of in utero infections and acuteness of infection.

Increased in: IgM is a major diagnostic criterion of myeloma. Increased IgM (with other immunoglobulins) may develop in inflammatory/infectious conditions. IgM is characteristically elevated in primary biliary cirrhosis.

Info: Macroglobulins produced in Waldenstrm disease are IgM, and may produce hyperviscosity syndrome. More than 2 g/dL of monoclonal The majority of rheumatoid factors are IgM. (1), (6)

IgG Total Antibodies

What is it: Immunoglobulin G is the most abundant immunoglobulin in the body. It is made by the plasma B cells as a secondary immune response after IgM.

Function: Quantitation of IgG is used to evaluate humoral immunity, monitor therapy in IgG myeloma, evaluate patients with lymphoma and a propensity to infections.

Increased in: IgG levels will be increased in immunocompetent individuals responding to a wide variety of infections or inflammatory insults. IgG specific antibody can now be demonstrated for numerous organisms, and when coupled with IgM specific antibody, can give an accurate diagnosis of acute or chronic infection.

Decreased in: Significant decreases in IgG level, on either a congenital or acquired basis, increase susceptibility to infection. Thus, patients with repeated infection should have their immunoglobulins, and specifically IgG, measured.

Info: If samples containing macroglobulins, cryoglobulins, or cold agglutinins are handled at incorrect temperatures, false low values may result. Immunoglobulin G is the major antibody containing protein fraction of blood. Therapy with exogenous gamma globulins may be efficacious in such patients. Today, a major cause for a polyclonal increase in IgG is the acquired immunodeficiency syndrome. Monoclonal IgG can be demonstrated in many cases of multiple myeloma. 3 g/dL of monoclonal IgG is a major diagnostic criterion for myeloma. Oligoclonal IgG can be seen in multiple sclerosis and some chronic hepatitides. A monoclonal gammopathy may be present when the total IgG value is in the normal range. While many of these patients do not have multiple myeloma, evaluation of these patients for evaluation of the gammopathy and the presence of Bence Jones protein in urine is important. (1), (6)

IgE Total Antibodies

What is it: Immunoglobulin E is an antibody only found in mammals and plays an important part in allergies, parasitic worms and some parasites.

Function: Immunoglobulins of the IgE class play an important role in mediating the atopic reactions that occur when sensitive individuals are exposed to allergens. The majority of IgE molecules in serum are bound to the surface of mast cells and basophilic granulocytes. The interaction of allergens with the cell-bound allergen-specific IgE causes these cells to release histamines and other vasoactive substances, thereby initiating the allergic reaction.

Tested for: Used primarily to evaluate immunoglobulin status in possible atopic disease, however normal IgE levels do not exclude allergic phenomena. Since IgE myeloma is extremely rare, the clinical utility of measuring IgE levels generally involves its role as the mediator of the allergic response.

Increased in: Approximately 50% of individuals with allergic rhinitis or asthma will have elevated levels of IgE. However, a large number of individuals with allergy and elevated levels of IgE to specific allergens will have normal levels of total IgE. Studies have indicated that total IgE levels are often elevated in patients with atopic dermatitis and the concentration of IgE tends to correlate with severity of eczema. Total IgE levels can also be elevated in patients with parasitic infections, allergic bronchopulmonary aspergillosis, or immunodeficiency. (1), (6)