Suppression of human granulocyte-macrophage colony formation in vitro by natural killer cells

This study has demonstrated the ability of human bone marrow natural killer (NK) cells to inhibit the formation of granulocyte-macrophage colonies from autologous bone marrow derived committed progenitors in vitro. NK cell activity was demonstrated in all marrow samples and could be significantly increased by pretreatment of the bone marrow mononuclear cells with IFN-alpha. Bone marrow preincubated with IFN-alpha produced significantly fewer colonies in both Day 7 and Day 14 colony assays compared with untreated marrow. Removal of active NK cells by Leu 11b and complement significantly increased the number of colonies observed in both Day 7 and Day 14 assays, but this was not the case when NK cell-depleted marrow was treated with IFN-alpha prior to the GM assays. These results have further shown that NK cells and IFN-alpha are involved in regulating granulopoiesis by demonstrating that IFN-alpha can inhibit granulocyte/macrophage colonies in the presence or absence of NK cells in the bone marrow.