The potential of human mast cell progenitors to differentiate into mature mast cells remains after prolonged culture with flt3 ligand, interleukin-3 or granulocyte-macrophage colony stimulating factor

Stem cell factor (SCF) plays a key role in the development of mast cells fr om haemopoietic progenitor cells. In this study we have investigated the ef fect of the early acting haemopoietic cytokines flt3 ligand (FL), IL-3 and GMCSF on the SCF-dependent differentiation of mast cells from cord blood mo nonuclear cells. By using delayed addition of SCF, we examined the potentia l of mast cell progenitors to keep their capacity to differentiate into mas t cells after exposure to factors Signalling differentiation into other lin eages. Culture with either cytokine for 3 weeks before transfer to SCF-cont aining medium resulted in the development of mast cells in all cultures, Th e appearance of mast cells was attenuated when the cells had been in cultur e with IL-3 or GM-CSF prior to culture in SCE compared to cultures exposed to SCF alone for 7 weeks. However, a proportion of the cells had not lost t he capacity to develop into mast cells. in contrast, in cultures initiated with FL and transferred to medium containing SCE the same amount of mast ce lls developed as in the SCF cultures. Thus, cells committed to the mast cel l lineage appear to be resistant to the lineage directives of IL-3 and GM-C SF and keep their potential to differentiate into mature mast cells.