The NeoR transgene is expressed late after transplantation. (A) Synopsis of ex vivo GMC G418 reselection and cloning. The process consists of a 7-day polyclonal (CD3-CD28 beads + IL-2) expansion followed by a 5-day selection in the presence of G418 before cloning. A representative agarose gel electrophoresis of qualitative NeoR PCR is shown. When possible, QPCR for the NeoR gene was applied after the selection step to quantify the selection efficiency. After cloning, screening was performed with both qualitative PCR assays to confirm the presence of the NeoR and HSV-tk genes. (B) Representative 2% agarose gel electrophoresis of screening. Except for 1 clone positive for the truncated form of the HSV-tk gene (311 bp of PCR product), all clones were HSV-tk⁻/NeoR⁺. Vertical lines have been inserted to indicate a repositioned gel lane.