|Year : 2002 | Volume
| Issue : 6 | Page : 438
Medline and key words: Myths and reality
Objective: To investigate the direct and the indirect effects of flt3 ligand (FL) on hematopoiesis.
Methods: Mononuclear cells from human cord blood were plated in methylcellulose medium containing different cytokines for inducing hematopoietic colony formation. Dendritic cells were induced from the mononuclear cells with a cytokine cocktail with or without recombinant human soluble FL (rhFL; 100ng/ ml). The flt3 receptors on the surface of a human microvascular endothelial cell line (ECV) were analyzed by flow cytometry. The proliferation of ECV stimulated by FL was measured with the microculture tetrazolium assay. We also measured the level of FL in the supernatant of ECV cultures.
Results: RhFL stimulates colony formation from cord blood when used as sole stimulant. FL in combination with other cytokines increased colony formation significantly. The number of DC was approximately 2.5 times higher when rhFL was used. RhFL stimulates the proliferation of ECV on which flt3 receptors is expressed. Furthermore, ECV secretes FL and this effect is augmented by tumor necrosis factor-?(?(TNF( ) and reduced by glucocorticoid.
Conclusions: FL enhances hematopoietic colony formation and DC proliferation from human cord blood cells. FL not only stimulates the proliferation of ECV, but it is also secreted by ECV. It appears that FL may act as an autocrine growth cytokine of endothelial cells.
Source of Support: None, Conflict of Interest: None