Complete eradication of lymphoma by anti-CD19–CAR-transduced T cells only occurred when mice were irradiated before adoptive T-cell transfer. (A) Mice received 5 Gy of TBI, and later the same day the mice were injected intraperitoneally with 38c13 lymphoma cells. The next day, the mice were divided into 4 treatment groups. One group was injected intravenously with 1D3-28Z.1-3–transduced T cells. Mice in this group received IL-2 on the day of T-cell transfer and the next day. A second group received T cells that were transduced with the control CAR SP6-28Z.1-3 plus IL-2. A third group received IL-2 alone, and a fourth group was left untreated. Each group included 5 mice. The P value of .002 refers to the comparison of the group that received 1D3-28Z.1-3–transduced T cells plus IL-2 to the group that received SP6-28Z.1-3–transduced T cells plus IL-2. The results from 1 of 2 experiments with nearly identical results are shown. (B) Mice were separated into 4 groups. The Radiation + IL-2 group received 5 Gy of TBI followed by an intraperitoneal injection of 38c13 cells. The Radiation + IL-2 group was injected intravenously with 1D3-28Z.1-3–transduced T cells the day after lymphoma injection. A dose of IL-2 was administered immediately after the T-cell injection, and a second dose of IL-2 was administered 1 day later. The No radiation group was treated identically to the Radiation + IL-2 group, except that TBI was not administered. The No IL-2 group was treated identically to the Radiation + IL-2 group, except that phosphate-buffered saline injections were administered in place of IL-2 injections. The No treatment group was left untreated. There were 5 mice in each group, except the No treatment group that included 4 mice. There was 100% survival of both the Radiation + IL-2 group and the No IL-2 group. The results are from 1 of 2 nearly identical experiments. The P value of .002 is for the comparison of the Radiation + IL-2 group to the No radiation group.