Beta-2-microglobulin protein (119 aa, ~14 kDa) is encoded by the human B2M gene. This protein plays a role in immune responses and is a key component of major histocompatibility complex class I molecules. The protein is localized to the surface of cells and is utilized as a prognostic marker in persons with cancers that involve white blood cells. The polypeptide is also used as a marker in kidney damage diagnosis and in the detection of viral infection. [ ]