The erythropoietic stimulating activity of normal mouse serum: effect on erythroid precursors from different haematopoietic tissues and suggested role of accessory cells.

The addition of normal mouse serum (NMS) to mouse bone marrow cell cultures was found to stimulate the growth of late erythroid precursors (CFU-E). The stimulating activity was called Erythropoietic Stimulating Cofactor (ESCF) (Blanchet et al 1984). In this article, we report that CFU-Es from foetal liver are not sensitive to serum addition, in contrast to CFU-Es from bone marrow or spleen taken from the same foetuses. When foetal liver cells were co-cultured with irradiated adult bone marrow cells, addition of NMS stimulated the foetal liver CFU-Es, suggesting that ESCF acts via some accessory cells not present (or in too low a frequency) among foetal liver cells. Moreover, NMS should be added at onset of adult bone marrow cell culture to be fully stimulatory. In addition, a very large increase (by a factor of 5 to 7) was observed for CFU-Es from spleen and bone marrow from 6- to 20-d-old newborn mice. This high sensitivity was correlated with a post-natal anaemia. We propose the existence of two different CFU-E population, one stimulated by the accessory cells, the other not, the proportion of which could be modified in response to anaemia.