PDCD1 and neoplasm: Three TCR pairs from T-iPSC clones whose TCRβ were not detected in the PD-1+ 4-1BB+ population, one TCR pair from a clone whose TCRβ was very low frequency (0.16%; Supplementary Table S1), and the PIR-TCR IV (Fig. 5B) as positive control were tested for specificity against autologous tumor cells.