Inhibition of the growth of IL-3-dependent mast cells from murine bone marrow by recombinant granulocyte macrophage-colony-stimulating factor.

The mouse mast cell line PT-18 demonstrates [3H] thymidine uptake in the presence of either mouse IL-3 or mouse recombinant granulocyte-macrophage CSF (rGM-CSF). Experiments were thus undertaken to determine whether rGM-CSF would affect IL-3-dependent growth of mast cells from mouse bone marrow cells (BMC). BMC placed in liquid culture containing 50 U/ml of IL-3 gave rise to cultures containing up to 95% mast cells by 2 to 3 wk. The rise in percentage of mast cells was accompanied by an increase in total cell-associated histamine. In contrast, BMC grown in the presence of 50 U/ml of rGM-CSF gave rise to cultures containing primarily macrophages and granulocytes with less than 1% mast cells. The addition of increasing amounts of rGM-CSF to BMC cultures grown in the presence of IL-3 resulted in a decrease in the number of mast cells present in culture at 2 to 3 wk. Cells other than mast cells in these cultures consisted principally of granulocytes and macrophages. The rGM-CSF-related inhibition of mast cell growth was not abrogated by the addition of indomethacin to cultures. Granulocyte-macrophage cell populations added to IL-3-containing cultures did not inhibit mast cell growth. The suppressive effect of rGM-CSF on IL-3-dependent mast cell growth may indicate an important role for GM-CSF in the down-regulation of mast cell proliferation in tissues.