Fig. 6

Immunofluorescence staining of Raji cells for confirmation of binding activity and internalization of scFv–apoptin. Raji cells were incubated with scFv–apoptin at 4 °C (5 µg/mL) (a), RFB4 at 4 °C (500 ng/mL) (b), scFv–apoptin at 37 °C (c), and RFB4 at 37 °C (d). After 2 h of incubation, cells were washed, fixed, permeabilized and treated with anti-6XHis-tag antibody and FITC anti-mouse IgG. Observation under the fluorescence microscope revealed cell surface binding and internalization (indicated by arrows) of the fusion protein