Characterization of purified human erythroid-potentiating activity.

Erythroid-potentiating activity (EPA), purified from serum-free medium conditioned by the Mo human T-lymphoblast cell line, is a 28,000 dalton glycoprotein. Removal of carbohydrate from EPA by digestion with endoglycosidase F generates a protein with an apparent molecular weight of 18,000. We have used purified EPA to develop rabbit antisera which neutralize the burst-promoting activity of purified EPA. These antisera immunoprecipitate a 28,000-dalton glycoprotein from metabolically labeled Mo cells. Purified EPA stimulates murine and human BFU-E and CFU-E but not myeloid or macrophage colonies.