Enhancement of erythroid colony formation in vitro by spleen extract from irradiated rats

The effect of spleen extract from irradiated rats on CFU-e and BFU-e colony formation of rat bone marrow cells was investigated by using modified plasma clot culture media. In the presence of erythropoietin (Ep), CFU-e colony formation peaked at 48 hr of culture, and the Ep-induced increase of CFU-e colonies was dose-dependent. The addition of spleen extract enhanced the colony formation more than two-fold in the Ep-containing culture. BFU-e colony formation was also enhanced by the addition of spleen extract. These results indicate that spleen extract from irradiated rats contains factor(s) which stimulates the proliferation of erythroid progenitors.