Beta-2 microglobulin is a protein that is found on the surface of nearly all the cells in the body. The protein is shed by the cells into the blood, especially the B lymphocytes and tumor cells. Protein is also present in most body fluids. The levels of protein present rise with conditions that increase cell production or destruction, or trigger a response from the immune system. This test measures the presence of beta-2 microglobulin in the blood. Beta-2 microglobulin is present in high levels in the blood with cancers like multiple myeloma, lymphoma, and other inflammatory infections and disorders like
HIV and
CMV. Since the level of beta-2 microglobulin rises with blood cell cancers, it is useful as a tumor marker. ‘ The beta-2 microglobulin level may also be higher in the cerebrospinal fluid sample of people that have blood cancer that has spread into the brain. It may also be higher in some chronic disorders like
multiple sclerosis and other viral infections like HIV. On the other hand, in the kidneys, the test passes via the glomeruli, which are the blood filtering units, and is absorbed into the renal proximal tubules, which are structures that reabsorb water, proteins, minerals, and other substances. In general, small amounts of B2M are detectable in the urine, but when these structures get damaged, the B2M concentrations increase because the ability to reabsorb the protein goes down.