á2-Microglobulin from Human Urine, 500ug

β-2-microglobulin (β2-M) is a polypeptide that associates with the heavy chain of class I major histocompatibility complex (MHC) antigens on the cell surface. The interaction is dynamic and plays a critical role in the stability of the MHC antigens and their ability to present peptide antigens in CD8+ cells. To study the effect of β2 microglobulin , mice models deficient for the β2 microglobulin gene have been engineered. These mice demonstrate that β2 microglobulin is necessary for cell surface expression of MHC class I and stability of the peptide binding groove. In the absence of β2 microglobulin, very limited amounts of MHC class I (classical and non-classical) molecules can be detected on the surface whereas in the absence of MHC class I, CD8 T cells cannot develop. Low levels of β2 microglobulin can indicate non-progression of HIV. A transient complex of MHC heavy chain and β2-Microglobulin is known to be assembled into the TAP molecule (transporter associated with antigen processing) through interactions with a number of chaperones. Binding of processed peptide releases the Class I-β2-Microglobulin complex to the cell surface. Absence of binding leads to degradation in the proteasome.