FLK-2/FLT-3 ligand regulates the growth of early myeloid progenitors isolated from XXXX fetal liver.

@entity1 @entity6826 @entity54854 @entity7801 @entity11601 @entity3053 @entity2772 @entity2280 @entity2841
The effects of the recently identified @entity7801 / @entity11601 (FL) on the growth of purified @entity1 fetal liver progenitors were investigated under serum-deprived culture conditions. FL alone was found to stimulate modest proliferation in short-term cultures of @entity2280 ++ @entity3053 + lineage (Lin)- light-density fetal liver (LDFL) cells and the more primitive @entity2280 ++ @entity3053 - Lin- LDFL cells. However, the low levels of growth induced by FL were insufficient for colony formation in clonal cultures. Synergism between FL and either @entity2841 ( @entity2841 ), @entity2772 ( @entity2772 ) or @entity6826 (KL) was observed in promoting the growth of high-proliferative potential (HPP) colony-forming cells (CF) and/or low-proliferative potential (LPP)-CFC in cultures of @entity2280 ++ @entity3053 + @entity54854 - and @entity2280 ++ @entity3053 - Lin- LDFL-cells. FL, alone or in combination with other cytokines, was not found to affect the growth of @entity2280 + Lin- LDFL cells, the most mature subpopulation of fetal liver progenitors investigated. The growth of the most primitive subset of progenitors studied, @entity2280 ++ @entity3053 - Lin- LDFL cells, required the interactions of at least two cytokines, because only very low levels of growth were observed in response to either FL, @entity2841 , @entity2772 or KL alone. However, the results of delayed cytokine-addition experiments suggested that individually these cytokines did promote the survival of this early population of progenitors. Although two-factor combinations of FL, KL, and @entity2841 were observed to promote the growth of early progenitors in a synergistic manner, neither of these factors was found to make fetal liver progenitors more responsive to suboptimal concentrations of a second cytokine. Only myeloid cells were recovered from liquid cultures of @entity2280 ++ @entity3053 - Lin- LDFL cells grown in the presence of combinations of FL, KL, and @entity2841 . These results indicate that FL is part of a network of growth factors that regulate the growth and survival of early hematopoietic progenitors.
