Co-expression of an antibody and a FM on the surface of transfected vector producing cells. 293T cells were transiently transfected with plasmids FUGW, pαCD20, pIgαβ, pFM, along with other standard packing plasmids to produce targeted FUGW/αCD20+FM vectors. The plasmid pAb was used in transfection to generate control vectors FUGW/Ab+FM. The transfection without FM plasmid was performed to generate the control vector FUGW/αCD20. The transfection with the standard envelope plasmid encoding VSVG was conducted to generate the non-targeting control vector FUGW/VSVG. (a) FACS analysis of GFP expression in vector producing cells. Solid line, analysis on transfected 293T cells; shaded area, analysis on 293T cells (as control) (b) Gating on GFP-positive cells, co-expression of an antibody and a FM is shown. Expression of an antibody and a FM were detected by using anti-human IgG antibody and anti-HA antibody, respectively.