Beta-2 - microglobulin (BMG, oncohematology)
Beta-2-microglobulin (Thymotaxin, B2M, B2M, Thymotaxin, Beta2-Microglobulin) is a protein present on the surface of nucleus containing cells as a light chain antigen of the major histocompatibility complex which is HLA.The protein is present on the surface of all cells, but its level in the blood reflects mainly the processes of degradation and repair of individual cell elements and proliferation of lymphocytes, in which it is present in large quantities. It is present in most physiologic fluids, and its level in serum is elevated in multiple myeloma, lymphoma, and inflammatory processes in the body.
In the kidneys, beta-2-microglobulin passes through the filters of the renal tubule capsules and is then absorbed by the renal tubules, which filter back water, proteins, vitamins, salts, and other substances necessary for the body. Normally, only a small amount of beta-2-microglobulin is found in the urine, but if the renal tubules are damaged or infected, its concentration increases due to decreased back absorption. After undergoing dialysis in patients suffering from kidney disease, beta-2-microglobulin may form long molecular chains that form deposits in joints and tissues, causing discomfort and pain. Such a condition is called amyloidosis associated with dialysis of beta-2-microglobulin.
Beta-2-microglobulin levels are sometimes elevated in cerebrospinal fluid in leukemia and lymphoma and in multiple sclerosis and HIV, which affect the brain.
Normally, only trace amounts of beta-2 microglobulin are detectable in the urine. Its half-life in plasma is from 20 min to 2 h.
Indications
Suspicion of “multiple myeloma” for staging the process and monitoring the effectiveness of treatment.
In leukemia and lymphoma to predict further progression of the disease.
In symptoms of renal dysfunction to clarify the lesion of the renal tubule capsule or renal tubules.
Examination of patients with transplanted kidneys and patients who have been in contact with elevated concentrations of cadmium and mercury.
Interpretation
An elevated beta-2-microglobulin level indicates the presence of pathology, but does not diagnose any disease. The results of the analysis reflect the activity of the disease and the size of the tumor mass.
A high level of beta-2-microglobulin in multiple myeloma, leukemia or lymphoma indicates an unfavorable prognosis of the disease.
A decrease in the concentration of this protein during therapy for multiple myeloma indicates a positive response to treatment, while unchanged or increasing levels indicate ineffective therapy.
Increased levels of beta-2-microglobulin after kidney transplantation may indicate the beginning of rejection of the artificial organ. Meanwhile, elevated beta-2-microglobulin levels due to exposure to high concentrations of cadmium and mercury may indicate the onset of renal dysfunction.
What can affect the result?
Diseases associated with an increased rate of cell formation or death, severe infectious and viral diseases (cytomegalovirus infections), certain factors that activate the immune system (inflammatory processes and autoimmune disorders) may be the cause of elevated beta-2-microglobulin levels.
Medications such as lithium, cyclosporine, cisplatin, carboplatin, and aminoglycoside antibiotics contribute to increased beta-2-microglobulin concentrations in blood or urine.
Modern nuclear medicine procedures and use of X-ray contrast agents can affect the results of the test as well.