Clinical trials demonstrate that autologous T cells persist longer than allogeneic products in treating B-cell acute lymphoblastic leukemia (B-ALL). With allogeneic CAR-T cells, only 14% of patients had detectable CAR-T cells after 42 days; only 1 patient exhibited persistence beyond 120 days . In contrast, the median persistence of tisagenlecleucel (autologous CAR-T cell medication) was 168 days, with some CAR-T cells persisting longer than 20 months . Other in vivo trials of relapsed/refractory ALL in humans demonstrated the presence of cytokine-release syndrome (CRS) after CAR-T cell treatment. CRS is indicated by high amounts of inflammatory cytokines such as interleukin-6 (IL-6) and interferon-γ (IFN-γ) and can become life-threatening . In a retrospective study, many more patients experienced severe CRS (Grade ≥ 3) from autoCAR treatment than alloCAR treatment . The median peak IL-6 level from the autoCAR cells (161.6 pg/mL) exceeded the peak level from the alloCAR group (38.7 pg/mL) . The overall remission rate was similar, with the complete remission (CR) rate being 88.2% for the autoCAR group and 100% CR rate for alloCAR . However, a contrasting prospective study found CRS occurring in 57% of patients treated with autoCAR-T cells and 91% of those administered with alloCAR-T cells . The study dosed seven children and 14 adults with UCART19, an allogeneic CAR-T therapy used to treat B-ALL . Not only did 19 patients (91%) suffer from CRS, but grade 1 acute skin GvHD occurred in 2 patients and grade 1 or 2 neurotoxicity occurred in eight patients (38%) . Thus, more research is necessary to determine the relationship between CAR-T cell source and the risk of CRS and other adverse events.