Characterization of human beta2-microglobulin by isoelectric focusing

b2-Microglobulin (B2M) isolated from the urine of normal subjects and patients with cadaveric renal transplantation, showed 2 homologues by isoelectric focusing, one with a pI 5.3, the other with a pI 5.7. These proteins show identical molecular weights by dextran gel filtration and sodium dodecyl sulfate acrylamide gel electrophoresis. The immunogenic reactivity demonstrates partial identity using antiserum to human B2M from 2 different sources.