The Selective Membrane Filtration of an ESF-generating Factor (EGF) in the Presence of Erythropoietin (ESF)

A mixture of an erythropoiesis stimulating factor (ESF) and an ESF-generating factor (EGF), isolated from the urine of a patient with paroxysmal nocturnal hemoglobinuria (PNH), was separated by selective membrane filtration. The optimum pH for activity of the EGF fraction from the urine of the PNH patient was about 7.4, the same as that previously found for the EGF from the urine of a patient with an anemia secondary to multiple myeloma (MM). The urine from the PNH patient contained an ESF that appeared larger than EGF, whereas the urine from the MM patient did not; the urine from both patients, however, contained an ESF that appeared smaller than EGF as previously noted.