Beta-2-microglobulin (B2M) is a 12-14 kDa protein that is a subunit of the major histocompatibility complex (MHC) class I. Human beta 2 Microglobulin associated with HLA Class I antigens are expressed on many types of cells including lymphocytes, thymocytes, monocytes, granulocytes, platelets, endothelial cells, and epithelial cells, but is absent on erythrocytes. Beta-2 microglobulin is also found in free form in the plasma. The amino acid sequence of Beta-2-microglobulin is homologous to the constant regions of immunoglobulin heavy and light chains, with a predominantly beta pleated sheet structure. The protein is ubiquitously expressed in the cytoplasm, and is involved in antigen processing and presentation. Beta-2-microglobulin also plays a role in TCR signaling, and downstream signaling in naive CD8+ cells. Beta 2-microglobulin is encoded by the B2M gene located on chromosome 15. A mutation in the Beta-2-microglobulin gene has been shown to result in hypercatabolic hypoproteinemia. Levels of beta 2 microglobulin can be used to assess renal function in kidney transplant recipients. Beta-2-microglobulin that protein can be used as a prognostic marker for HIV infection.
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Protein Aliases: B-F; B2-microglobulin; beta chain of MHC class I molecules; beta-2-microglobin; Beta-2-microglobulin; Beta-2-microglobulin form pI 5.3; Beta2 microglobulin; MHC Class I; microglobulin beta-2; Orla-B2m
Gene Aliases: B2M; CDABP0092; HDCMA22P; IMD43
UniProt ID: (Human) P61769
Entrez Gene ID: (Human) 567
Molecular Function: major histocompatibility complex protein