ingredient information
Beta Microglobulin
AAA
ß2 microglobulin also known as B2M is a component of MHC class I molecules, which are present on all nucleated cells (excludes red blood cells).[1][2] In humans, the ß2 microglobulin protein[3] is encoded by the B2M gene.[2][4] Contents [hide] 1 Structure and function 2 Clinical significance 3 References 4 Further reading 5 External links [edit] Structure and function Schematic representation of MHC class Iß2 microglobulin lies lateral to the a3 chain on the cell surface. Unlike a3, ß2 has no transmembrane region. Directly above ß2 (i.e. away from the cell) lies the a1 chain, which itself is lateral to the a2. ß2 microglobulin associates not only with the alpha chain of MHC class I molecules, but also with class I-like molecules such as CD1 and Qa[disambiguation needed ]. An additional function is association with the HFE protein, together regulating endocytosis of iron into intestinal cells. Loss of this function causes iron excess and hemochromatosis. [edit] Clinical significanceIn patients on long-term hemodialysis, it can aggregate into amyloid fibers that deposit in joint spaces, a disease known as dialysis-related amyloidosis. Mice models deficient for the ß2 microglobulin gene have been engineered. These mice demonstrate that ß2 microglobulin is necessary for cell surface expression of MHC class I and stability of the peptide binding groove. In fact, in the absence of ß2 microglobulin, very limited amounts of MHC class I (classical and non-classical) molecules can be detected on the surface. In the absence of MHC class I, CD8 T cells cannot develop. (CD8 T cells are a subset of T cells involved in the development of acquired immunity.)Low levels of ß2 microglobulin can indicate non-progression of HIV. Levels of beta-2 microglobulin can be elevated in multiple myeloma and lymphoma,[5] though in these cases primary amyloidosis (amyloid light chain) and secondary amyloidosis (Amyloid associated protein) are more common. the normal value of beta-2 microglobulin ranges from( 1 - 2.1 )