Terminally differentiated T cells partially acquire memory T-cell properties upon PRDM1 knockout. (A-B) CD19-targeting CAR-T cells were electroporated with Cas9/sgRNA against PRDM1 following repeated stimulation by NALM-6 and analyzed for memory T-cell markers. Representative flow cytometry plots (A) and the frequency of the indicated populations are shown (B) (n = 4, ordinary one-way ANOVA with multiple comparisons test). Representative data of 2 experiments. (C,D) Human T cells knocked out with PRDM1 after repeated stimulations were infused into irradiated NSG mice (n = 6 mice per group). The frequency of human T cells in the PB was monitored at the indicated time points (D) (n = 6, Mann-Whitney U test). (E-I) TIL dissociated from tumor samples were expanded and then ablated with PRDM1. Representative flow cytometry plots analyzing memory T-cell phenotypes (F) and the frequency of CD8⁺ T cells expressing the indicated molecules (G) (n = 8 samples, repeated measures of one-way ANOVA with multiple comparisons test). (H) The expression of TCF7 was analyzed by intracellular flow cytometry 5 days after electroporation. Mean fluorescence intensity within the CD8⁺ T-cell population was shown (n = 5, paired 2-tailed Student t test). (I) Expanded TILs were restimulated by K562 expressing anti-CD3 mAb and 41BBL, and the production of IL-2, IFN-γ, and TNF-α was analyzed by flow cytometry (n = 5, paired 2-tailed Student t test).