Learn something new every day More Info... by email
Beta-2 microglobulin (b2m) is a naturally occurring protein in the human body. It is one of two polypeptide chains that make up the structure of a major histocompatibility complex (MHC) Class I molecule. Certain characteristics of b2m make it suitable for detecting tumor cells, especially in blood and kidney cells. B2m also has been used to evaluate kidney function following a kidney transplant operation, and as a prognostic tool for immune system-related diseases.
This large protein belongs to a class of histocompatibility molecules, which are glycoproteins expressed at the surface of nucleated white blood cells in vertebrates. MHC Class I molecules such as b2m are useful for detecting incompatible or genetically different cells within the body. Some key characteristics of beta-2 microglobulin are that it has no transmembrane region, associates with the alpha chain of MHC Class I molecules by non-covalent bonds and associates with the human hemochromatosis (HFE) protein. Normal levels of beta-2 microglobulin range from 1 to 2.1 micrograms per milliliter (µg/mL); upper normal range values are 2.0 to 2.5 µg/mL.
An MHC Class I molecule consists of two polypeptide chains, a long alpha chain on the left and a shorter chain on the right that is beta-2 microglobulin. Histocompatibility molecules also are referred to as antigens because of their ability to elicit an immune system response. Basically, for a tissue transplant to be successful, the MHC of the tissue’s cells must be compatible between the donor and the recipient. Additionally, if an unhealthy cell containing foreign material from a disease, virus or bacteria is detected, then the MHC Class I molecules will flag them as a signal for the immune system to attack the cells containing foreign proteins. In clinical studies, the level of beta-2 microglobulin production is directly associated with lymphocyte activation, a signature immune system response.
B2m molecules have been targeted in cancer treatment and immune system disorders in which T-cells are involved. Clinical studies with b2m-deficient mice have demonstrated an important role of beta-2 microglobulin in cellular surface expression of MHC Class I molecules and peptide binding. Without peptide binding and subsequent protein synthesis, the production of certain immune system-related cells, including T-cells, is halted when b2m is absent. Immunology assays have been developed using b2m as a tumor marker.
A physician or oncologist may perform a b2m test to get a general idea of how much cancer may be present in a patient. Elevated b2m levels can indicate multiple myeloma, lymphoma or leukemia. Both blood and urine tests for beta-2 microglobulin have been used for patients with kidney disease following a kidney transplant. B2m can distinguish between glomular and tubular kidney disorders. In rare cases, b2m tests are used to evaluate the effects of a disease on the central nervous system.
One of our editors will review your suggestion and make changes if warranted. Note that depending on the number of suggestions we receive, this can take anywhere from a few hours to a few days. Thank you for helping to improve wiseGEEK!