Effect of prednisolone on the growth of human bone marrow cells in vitro.

The addition of prednisolone to autostimulatory cultures of human bone marrow in agar results in the formation of an increased number of granulocytic aggregates. The effect is dependent on the concentration of cultured cells and does not occur at low cell concentration. The increase in aggregate numbers is maximal early in the culture and occurs at steroid concentrations which are comparable with pharmacological levels. Prednisolone directly inhibits the responsiveness of granulocytic precursors to colony-stimulating activity (CSA) and it is suggested that the stimulatory effect is indirect and may be caused by a steroid action on mediator production. These findings may be relevant to the polymorphonuclear leucocytosis induced by glucocorticoids.