Overall, CART cells derived from untreated patients displayed a higher percentage of PD-1 on their cell surface when compared to HDs [IL-7/IL-15: 23 ± 6% PD-1+ CART cells (HDs) vs. 47 ± 15% (untreated CLL patients); IL-2: 23 ± 7% PD-1+ CART cells (HDs) vs. 47 ± 22% (untreated CLL patients)]. The gene discussed is IL2; the disease is B-cell chronic lymphocytic leukemia.