Figure 2.

Integration site and TCR analysis on safety switch gene-modified T cells. The safety switch transgene is integrated into the host cell genome, with 1–3 copies of integrants per cell. The region of the genomic DNA in which the transgene integrates (indicated by a unique color) is unique to each integration event and all progenies from that cell can be identified through the unique integration site. Similarly, each T cell bears a unique TCR (indicated by a unique color), which is passed on to all progenies. However, two cells bearing the same TCR may be separately gene-modified, resulting in two clones of T cells which bear the same TCR but with different integration site. Surface markers, for example ΔCD19 or ΔLNGFR, enable identification of safety switch gene-modified T cells by flow cytometry and can be used for cell sort before TCR sequencing. The concurrent analysis of TCR and integration site can provide high resolution data on the clonal origin of safety switch gene-modified T cells.