Schematic diagram of retroviral display methodology. Retroviral packaging cells were transfected with the plasmid pREP8-mbSCF. The cells were converted to producers by transfection with a retroviral genome. The SCF protein synthesized by these cells is expressed on the cell surface and incorporated into virus particles as they bud through the plasma membrane. Modified from Access Excellence at the National Health Museum³⁰  with permission.