Humoral stimulation of hemopoietic progenitors from human fetal liver.

Hemopoietic cells from human fetal livers of 9-21 weeks gestation were cultured in semisolid media in vitro and in diffusion chambers implanted in mice. Myeloid colony formation in agar (CFU-C) was detected only in the presence of colony-stimulating factor. Formation of erythroid bursts in vitro was enhanced by addition of erythropoietin or erythroid-potentiating activity derived from a human T cell line (Mo). Fetal liver cells implanted in diffusion chambers gave rise to myeloid (CFU-DG) and occasionally to erythroid colonies. Administration of colony-stimulating factor derived from the T cell line to the host mice did not effect CFU-DG numbers. In contrast, a partially purified preparation containing erythroid-potentiating activity, caused a significant increase in the formation of CFU-DG. Similar stimulation was achieved by pretreatment of the diffusion chamber hosts with cyclophosphamide. None of these manipulations effected erythroid colony formation in diffusion chambers in mice.