In vitro inhibition of myelopoiesis by gold salts and D-penicillamine.

Leukopenia is one of the more serious side effects of gold and D-penicillamine therapy. We report that gold salts (gold thiomalate, gold chloride and gold thioglucose) and D-penicillamine suppressed the in vitro development of colonies of myeloid cells (macrophage, granulocyte and megakaryocyte) from progenitor cells in murine bone marrow; these drugs were also effective in inhibiting the development of macrophage and granulocytic colonies in human bone marrow. The drugs generally required concentrations of 10(-5) M in the murine system, whereas they were active at 10(-7)-10(-8) for the human progenitor cells. The disease suppressive activity of gold salts and D-penicillamine could result in part from the reduction of cell numbers in arthritic lesions; our findings would provide a mechanism for this possibility.