[Effect of activated monocytes on the growth of cloned granulocytic progenitor cells]

The humoral effect of resting and phorbol myristate acetate (PMA) preincubated normal monocytes on granulocytic progenitor growth in double diffusion chamber culture (CFU-dG) was assayed. The activation of monocytes by PMA was confirmed in NBT reduction test (increased formazan content) and by enhanced superoxide anions production compared with resting cells. The activatory and inhibitory effect of monocytes on granulocytic colony formation was cell-concentration dependent. The maximal CFU-dG growth promoting effects was seen at 5 X 10(4) of resting monocytes, whereas PMA-treated cells exerted their optimal stimulatory activity at lower cell number (2.5 X 10(4)). Further increase of monocyte concentration resulted in diminished CFU-dG proliferation. It is shown that the decline of colony count at high monocyte number was caused by indomethacin-dependent inhibitors.