Studies on the inhibitory effect of granulocytes on human granulocytopoiesis in agar cultures

In the present study, the inhibitory effect of blood granulocytes on granulocytic colony formation from human white blood cells was tested. Attempts were made to clarify the effects of granulocytes by plating increasing numbers of polymorphonuclear cells (PMN) by using granulocytes which had been inactivated by freezing, by studying the effect of PMN removal and by observing the effect of dilution of granulocyte inhibitors to ineffective levels at different time intervals after the onset of culture. It will be shown that colony formation is inhibited by an excess of PMN and that the inhibitor is produced only by viable PMN. There is no inhibition during the early phase of the culture, thus suggesting that the CFU-C itself is not the target cell for the inhibition of colony formation in agar culture, but rather the more mature precursor cells of granulopoiesis.