Beta2-microglobulin (ß2M) is a low molecular weight protein (11.8 kD) present on the surface of many cells. beta2-microglobulin exists in two forms; in free form or in membrane form, identified as the light chain of the major histocompatibility complex (MHC) class I.
Beta2-microglobulin is found in low concentrations in serum. Beta2-microglobulin is a first line marker for multiple myeloma and in B lymphocyte malignancy. Beta2-microglobulin assay also has clinical benefit for patients with kidney disorders and infectious diseases, including human immunodeficiency virus (HIV), inflammatory bowel disease (IBD), autoimmune disease and rheumatoid arthritis.