Effect of sera from various vertebrate species on mouse erythroid progenitor proliferation

Sera from different vertebrate species were tested for their stimulating activity upon mouse CFU-E growth. Crude sera were either naturally stimulating or toxic. Absorption on mouse blood and spleen cells or decomplementation removes or neutralizes the toxicity, probably mediated through natural anti-mouse antibodies. All but 2 sera tested (ox and sheep) were stimulatory. This stimulating activity was found to be either heat-sensitive or -resistant according to the sera. Upon chromatography on DEAE cellulose, 2 fractions were obtained which were both stimulatory. Whether these two stimulating activities correspond to different molecules or to only 1 absorbed on different serum proteins remains to be determined. These results confirm previous results obtained for mouse and human sera and suggest that this cross-reactive stimulating activity may have an important role in vertebrate erythropoiesis.