Consistent with post‐transduction observations CLL‐derived CAR T cells retained a more differentiated profile, with high frequencies of Tem and Tcm, while ALL‐derived CAR T cells preserved higher levels of Tn (CD4+ CAR T cells in C: CLL 0.9% ± 0.1 vs. ALL 2.9% ± 0.7; CD8+ CAR T cells in C: CLL 0.8% ± 0.3 vs. ALL 6.3% ± 2.8; P < 0.05 Mann–Whitney U test) and Tscm (CD8+ CAR T cells in P: CLL 10.7% ± 2.3% vs. ALL 23.2% ± 4.0; in C CLL: 8.6% ± 2.8 vs. ALL 19.5% ± 3.1; P < 0.05 Mann–Whitney U test). The gene discussed is CD4; the disease is acute lymphoblastic leukemia.