Humoral regulation of pluripotent stem cell differentiation.

Humoral regulators of CFU-S differentiation have been demonstrated in bone marrow of Ara-C treated animals. These factors are effective in vivo and are also capable of inducing erythropoietic differentiation of normal CFU-S in vitro. These results seem to indicate that the microenvironment acts at the committed stem cell level while the factors described in this paper act on the pluripotent stem cells.