Beta2 microglobulin, also known as B2M, is a component of MHC class I molecules, Involved in the presentation of peptide antigens to the immune system. B2M is a protein found on the surface of many cells and plentiful on the surface of white blood cells. Increased production or destruction of these cells causes B2M levels in the blood to increase. This increase is seen in people with cancers involving white blood cells, but it is particularly meaningful in people newly diagnosed with multiple myeloma. Multiple myeloma is a malignancy (cancer) of a certain kind of white blood cell, called a plasma cell. B2M Testing is done primarily when evaluating a person for certain kinds of cancer affecting white blood cells including chronic lymphocytic leukemia, non-Hodgkin's lymphoma, and multiple myeloma or kidney disease.