Extended Data Fig. 2: Expression of surface pre-TCR in T-ALL cell lines and primary samples.

(A) Representative pseudocolour plots of CD3 vs pTα expression in pre-TCR-expressing SupT1, and TCRαβ-expressing HPB-ALL and Jurkat human cell lines from three independent experiments, as assessed by reactivity with anti-CD3ε and anti-pTα monoclonal antibodies (left biparametric histograms). Representative monoparametric histograms on the right show surface pre-TCR expression levels analysed with anti-pTα monoclonal antibody plus goat anti-mouse FITC. Numbers indicate percentages of positive cells. Shaded histograms show background staining with an irrelevant isotype-matched antibody. (B) Representative CD3 vs TCRαβ expression of either primary human thymocytes from a single 17-weeks-old fetal thymus sample (upper left), or developing T cells derived either from two independent human CB HPC samples after 70 days of culture onto OP9-Jag2 cells (middle left), or from a single CD34⁺ human ETP sample after 18 days of culture in ATOs (bottom left). Pre-TCR expression levels of electronically gated CD3^lo TCRαβ^neg, TCRαβ⁺ and CD3^neg cells analysed with anti-pTα mAb plus biotin-coupled anti-mouse (Fab’)2 plus BV421-coupled streptavidin are shown in the monoparametric histograms on the right. Numbers indicate percentages of positive cells relative to background staining with an isotype-matched mAb.