Purification of erythropoiesis-stimulating activity (ESA) from one Actinomycetes strain

An Actinomycetes strain was found to produce a protein which stimulated the growth of murine erythroid progenitors in vitro. The protein was purified to homogeneity and was named Erythropoiesis-Stimulating Activity (ESA). ESA was an acidic glycoprotein with a molecular weight around 80,000. When mouse bone marrow cells were cultured in methylcellulose medium containing physiological concentrations of erythropoietin (0.048 units/ml), addition of ESA stimulated the growth of colony forming unit-erythroid (CFU-E) up to three-fold a in dose dependent manner. ESA was not active on the other hematopoietic progenitors.