The lentiviruses generated from these constructs were transduced into CD8 T cells and cultivated in the presence of IL-21, which yielded CAR T cells with modestly improved proliferation than was seen with IL-2 (Supplementary Figure 1A and 1B), while maintaining the same specific killing activity for CAIX+ RCC (Supplementary Figure 1C and 1D). The gene discussed is IL2; the disease is renal cell carcinoma.