Immunoelectrophoresis is a type of laboratory test used to identify certain protein molecules produced by the immune system. The test uses electric charge to separate molecules by applying an electric current to a gel containing a sample. The presence of an individual protein is then identified by applying an antigen specific to the molecule. The test is used to diagnose a variety of diseases, such as multiple myeloma, hepatitis and leukemia.
Immunoelectrophoresis is used in diagnosis and tracking the progress of disease because some diseases cause levels of antibody proteins, called immunoglobulins, to rise or fall. The immunoglobulins generally tested for are Immunoglobulin A (IgA), Immunoglobulin M (IgM) and Immunoglobulin G (IgG). These molecules make up the majority of blood serum immunoglobulins.
Immunoglobulin A plays an important role in preventing infection through the gastrointestinal tract, mouth and respiratory system, but it is also present in the blood. Immunoglobulin M is the immune system's initial response to antigen exposure, and levels of IgM are affected by vaccinations and infections such as hepatitis. IgM is also responsible for ABO blood group differences. IgG is the most common of the immunoglobulins and is produced when the body is exposed to a previously recognized antigen; this is why recent vaccinations can affect the IgM and IgG results of immunoelectrophoresis tests.
Immunoelectrophoresis test gels are kept under electric current for a specified time depending on the brand of test material used. Antigens to the individual immunoglobulins are added to the gel. The gel is then washed to remove loose, unbound protein and stained with a protein-specific stain. The areas to which the antigens bind are visually identifiable after the stain has been allowed to work for a specified time. When the sample test is compared to a control containing known levels of protein, a rough estimate of immunoglobulin levels can be made.
One of the advantages of the test is that it can be used to identify both monoclonal and polyclonal gammopathies. A monoclonal gammopathy is a disease state in which a single type of immunoglobulin is affected by the disease. A polyclonal gammopathy occurs when a disease causes changes in the levels of two or more immunoglobulins.
Immunoelectrophoresis is performed after another test, protein electrophoresis, indicates abnormal levels of immunoglobulins in blood serum samples or urine samples. The immunoelectrophoresis test is more specific than the protein electrophoresis test and can identify specific immunoglobulins. A disadvantage of immunoelectrophoresis is that results cannot identify the exact level of Ig molecules in a sample, so another procedure, immunofixation, may be used as a more sensitive alternative.