Isolation of human erythropoietin with monoclonal antibodies

Human erythropoietin was isolated from urine of aplastic anemic patients in a high yield with a simple purification procedure using an immunoadsorbent column of monoclonal antibodies and a Sephadex G-100 column. About 6 mg of erythropoietin was isolated from 700 liters of urine and the specific activity was estimated to be 81,600 units/mg of protein with an in vivo 59Fe incorporation assay method, using starved rats. Activity measurement of the extracts from sliced gels after sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the Western blotting technique revealed heterogeneity of the isolated erythropoietin, which is probably caused by variable amounts of carbohydrates attached to the polypeptide chain. Thirty amino acids in the NH2-terminal portion of the isolated hormone were sequenced.