Human leukocyte interferon preparation-mediated block of granulopoietic differentiation in vitro

We have recently reported that human leukocyte-interferon preparation (HLIF) blocks granulopoietic differentiation. In the current study, using suspension cultures, we further demonstrate that HLIF can effectively block granulopoietic differentiation, resulting in an accumulation of granulocyte-macrophage progenitor cells (GM-CFC), cluster-forming cells and the morphologically identifiable myeloid precursors. Using semisolid agar cultures, we have also demonstrated that the effect of HLIF on GM-CFC and cluster-forming cells is reversible and that human placental conditioned medium (HPCM), used as a source of colony-stimulating factor (CSF), can effectively counteract the effect of HLIF action on the granulopoietic precursors. The interferon preparation derived from human fibroblasts, on the other hand, was found to be less effective in blocking granulopoietic differentiation compared to HLIF; indicating a tissue-specificity of interferon action. These data suggest that HLIF may have a regulatory role in the control of granulopoietic proliferation and differentiation.