Characterization of circulating, expanded CAR-T cells. (A) The expanded CAR T-cell CD4/CD8 phenotype evaluated via flow cytometry for both CD19-CAR–Retro_ALLO and CD19-CAR–Lenti_ALLO. The memory phenotype, with identification of naive (N), CM, EM, and TEMRA subpopulations, was characterized via flow cytometry for the CD19-CAR–Retro_ALLO CD4⁺ (B) and CD8⁺ cells (C), and for the CD19-CAR–Lenti_ALLO CD4⁺ (D) and CD8⁺ cells (E).