Effects of interleukin-4 (IL4) on myelopoiesis: studies on highly purified CD34+ hematopoietic progenitor cells.

We studied the effects of interleukin 4 (IL4) on myelopoiesis supported by either granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage CSF (GM-CSF) or IL3 on purified CD34+ bone marrow progenitor cells. IL4 stimulates the colony-forming unit granulocyte (CFU-G) induced by G-CSF and inhibits all colony types supported by either IL3 and GM-CSF, although inhibition of CFU-M (macrophage) was significantly stronger than that of CFU-G and CFU-GM. When the cells were first incubated in liquid culture for 4 days in IL4, followed by agar culture in G-CSF, there was a significant increase in the number of CFU-G compared to cells which had been incubated in medium alone for 4 days before plating out in agar containing G-CSF. The inhibitory effects of IL4 on GM-CSF or IL3 supported colony formation, however, disappear with sequential incubation in IL4 in liquid culture followed by culture in agar with either GM-CSF or IL3.