Use

Beta-2-microglobulin (beta-2-M) is a small membrane protein associated with the heavy chains of class I major histocompatibility complex proteins and is present on the surface of all nucleated cells. Its small size allows beta-2-M to pass through the glomerular membrane; however, it is almost completely reabsorbed in the proximal tubules. Elevated beta-2-M levels in the cerebrospinal fluid (CSF) can be diagnostic in cases of non-Hodgkin lymphoma with central nervous system involvement. Increased CSF:serum ratios are observed in conditions such as aseptic meningoencephalitis, indicating possible neurologic processes including those associated with HIV infection and acute lymphoblastic leukemia. In the context of multiple sclerosis, the significance of beta-2-M measurement remains indeterminate.