Positive and negative effects of tumor necrosis factor on colony growth from highly purified normal marrow progenitors.

The effects of recombinant human tumor necrosis factor alpha (TNF alpha) on colony growth were studied using highly enriched progenitor cells from normal human bone marrow. Supplementation of TNF to culture resulted in a dose-dependent suppression of granulocyte colony-stimulating factor (G-CSF) induced granulocytic colony formation and also erythropoietin (Epo) induced erythroid burst formation. However, the number of erythroid bursts, stimulated by interleukin-3 (IL-3) plus Epo, increased when TNF was added at comparable concentrations. Further, TNF enhanced eosinophilic colony growth induced by IL-3 or granulocytic-macrophage colony-stimulating factor (GM-CSF). In GM-CSF cultures TNF (100-1000 U/ml) also induced granulocytic and macrophage colonies. The addition of neutralizing antibodies against G-CSF, GM-CSF, or interleukin-6 (IL-6) to culture did not abrogate the observed effects of TNF, so that stimulation of myeloid colony growth was unlikely to result from the secondary induction of G-CSF or GM-CSF. TNF therefore exerts favourable effects on hematopoietic progenitors responsive to the more primitive colony-stimulating factors (IL-3, GM-CSF) and potent negative effects on precursors reactive to the single lineage G-CSF and Epo. These contrasting effects of TNF suggest that TNF, when available to marrow progenitors at similar tissue concentrations, may drive hematopoiesis within the progenitor cell compartment into selected directions.