blood beta-2 microglobulin serum beta-2 microglobulin 2019-02-15T11:23:30Z CMO:0003040 The amount of beta-2 microglobulin (B2m) in a specified volume of serum, the clear liquid that separates from blood after it has clotted completely, i.e. blood plasma from which fibrinogen has been removed. B2m is found in association with the major histocompatibility complex (MHC) class I heavy chain on the surface of most cells and has a predominantly beta-pleated sheet structure that can form amyloid fibrils in some pathological conditions. VT:0005416 clinical_measurement_ontology sjwang