Beta-2 microglobulin

Beta-2 microglobulin is used by some centers as a prognostic factor and is particularly favored by the MD Anderson Cancer Center in Houston.

Bete-2 microglobulin is the small subunit of the MHC class I molecule. The MHC class I molecule is the same as the HL-A antigen that is present on the surface of almost all nucleated cells in the body. These HL-A antigens are the expression of self for every cell and it is because they are recognised as such that they and the peptides they carry are targeted by a foreign immune system. The beta 2-microglobulin is generally required for the transport of class I heavy chains from the endoplasmic reticulum (endoplasmic reticulum is the factory floor of the cell) to the cell surface.

Beta 2-microglobulin is present in small amounts in serum, and urine of normal people,the normal level varies from lab to lab, but up to 2.7 mg/dL is a figure given by Google. There is a lot of beta-2 M on lymphocytes. Therefore, anything that makes lymphocytes multiply can give a raised level. Virus infections, particularly infectious mononucleosus and CMV infections can do this.

The level of beta-2 M is one of the best prognostic factors for multiple myeloma but this exposes one of its problems. Renal damage is common in myeloma, but beta-2 M is excreted through the kidneys so there is a risk of a falsely high value. In lymphomas beta-2 M has been used as a prognostic factor as it has in CLL, but it measures two separate things: a] the amount of lymphoma or CLL present, and b] the rate of turnover of lymphoma or CLL cells. In early stage CLL it has never been tested as a means of predicting who in the future will need treatment.

There is no reference to turn to for how well beta-2 M performs as a prognostic factor in CLL. Although in terms of ease of use it has advantages few centers have adopted it.