Objective  To observe the proliferation of cord blood stem cells and detect their mRNA and protein levels of FL and IL3 after transfection of plasmid vector pIRES2-FL-IL-3.   Methods  The cell survival rate and proliferation of the cord blood stem cells were observed by dye staining and MTT methods after transfected by plasmid vector pIRES2-IL-3

pIRES2-FL or pIRES2-FL-IL-3. The mRNA and protein levels of FL and IL-3 were detected by RT-PCR and Western blot.   Results  No statistical difference on cell survival rate of cord blood stem cells was observed between those transfected by plasmid vector pIRES2-FL-IL-3 and their corresponding controls. The cell proliferation of cord blood stem cells transfected by pIRES2-FL-IL-3 was higher than those transfected by pIRES2-IL-3 or pIRES2-FL. The mRNA and protein levels of FL and IL-3 in the cord blood stem cells transfected by pIRES2-FL-IL-3 were higher than those in the normal cord blood stem cells

and those transfected pIRES2-IL-3 group or pIRES2-FL respectively.   Conclusion  The transfection of pIRES2-FL-IL-3 to the cord blood stem cells does not influence the cell survival rate but accelerates their proliferation. FL and IL-3 co-expression displays synergic effect on the proliferation of cord blood stem cells.