Retroviral gene transfer, rapid selection, and maintenance of the immature phenotype in mouse dendritic cells

We used the retroviral vector PINCO [which expresses the green fluorescent protein (GFP) as a selectable marker], to infect growth factor-dependent immature D1 dendritic cells (DC). The efficiency of infection in different experiments was between 5 and 30%, but subsequent cell sorting led to a virtually homogeneous population of GFP-positive cells. Retroviral infection did not modify the immature DC phenotype, as shown by the low expression of major histocompatibility complex and co-stimulatory molecules. Furthermore, the GFP-positive D1 cells underwent full maturation after lipopolysaccharide treatment, as indicated by a high expression of cell-surface MHC and co-stimulatory molecules, and also by strong stimulatory activity in allogeneic mixed lymphocyte reaction. The high efficiency of this retroviral system, the rapidity of the technique, and the possibility to overcome in vitro selection make this method very attractive for the stable introduction of heterologous genes into proliferating immature mouse D1 cells. Furthermore, this approach is suitable for functional studies of new DC-specific genes involved in DC maturation and survival.