Dual effect of monocyte-conditioned medium on in vitro hematopoiesis.

To investigate the effects of the conditioned medium on regulation of hematopoietic stem cells, serial volumes of monocyte-conditioned medium were added to the culture systems of CFUE and CFUC. Small volumes of the conditioned medium possessed stimulatory activity and large volumes inhibitory activity for both CFUE and CFUC. These findings suggest that the monocyte-conditioned medium regulates both CFUE and CFUC dualistically in accordance with the volume of the medium added to the culture system. The suppression of the growth of CFUE and CFUC by monocyte-conditioned medium was completely protected when the medium made in the presence of indomethacin was added. Monocyte mediated suppression was partially recovered when both monocytes and indomethacin were added. E series prostaglandins appear to be inhibitory mediators of monocyte and monocyte-conditioned medium mediated suppression, but some other mechanism seems to be involved in the monocyte mediated suppression.