β-2 microglobulin (beta-2)

β-2 microglobulin (beta-2)

Indications for β-2 microglobulin:

1. Monitoring of multiple myeloma, non-Hodgkin's lymphoma
2. Monitoring of patients with AIDS and after organ transplantation

β-2 microglobulin consists of 100 amino acids, molecular weight of 11 800 Da. Detected on the surface membrane of lymphocytes, macrophages, and some epithelial cells. β-2 microglobulin in low concentration is detected in many biological fluids:

• in serum
• in urine
• in saliva
• in amniotic fluid
• in cerebrospinal fluid

β-2 microglobulin passes freely through the membrane of the renal glomeruli and then reabsorbed in the proximal renal tubules.

The decrease in glomerular filtration leads to a rise in the level of serum β-2 microglobulin, and impaired function of renal tubules leads to its excretion in the urine. The normal level of β-2 microglobulin:

• in serum – 0,8-2,4 mg/l
• in cerebrospinal fluid – 0,8-1,8 mg/l
• in urine – 0,02-0,3 mg/l

The level of β-2 microglobulin increases with myeloma, non-Hodgkin's lymphoma, various autoimmune diseases, impaired cellular immunity (e.g., AIDS), conditions after organ transplantation. In patients with leukemia increased level of β-2 microglobulin in the cerebrospinal fluid suggests the involvement in the pathological process of the central nervous system.

Testing of β-2 microglobulin in serum and urine is mainly conducted in the diagnosis of glomerulonephritis and tubular nephropathy. In multiple myeloma this marker is the most useful prognostic indicator, independent of the concentration of monoclonal immunoglobulin.