Kidney cell lysates contain an activity that stimulates mature erythroid burst-forming-unit (mBFU-E) proliferation

This study reports the detection of an activity that stimulates the development of a subclass of burst-forming unit-erythroid (BFU-E) progenitors giving rise to small bursts in semi-solid cultures established in the presence of saturating concentrations of erythropoietin. These progenitors are considered to be mature BFU-E. The activity is found in extracts from kidney cells and appears to be physiologically regulated as it was respectively enhanced and decreased in kidneys from anemic and polycythemic mice. The disappearance of activity in kidney-cell extracts during long-term polycythemia correlated with an accumulation of mature BFU-E in the spleen and bone marrow of polycythemic mice. Using specific neutralizing antibodies and in vitro tests, we also show that this activity is different from hemopoietins known to share burst promoting activity (Interleukin-3 [IL- 3], granulocyte-macrophage colony-stimulating factor [GM-CSF], Interleukin-4 [IL-4], erythropoietin [EPO], human interleukin for DA cells [HILDA]) and that it can stimulate erythroid differentiation in long term bone marrow cell cultures.