IL-15 administration increases GVT activity in recipients after an allo BMT. Lethally irradiated (1300 cGy) B6 recipients received transplants of B10.BR TCD-BM cells (5 × 10⁶) with the addition of B10.BR splenic T-cells (0.5 × 10⁶) on day 0. Recipients also received EL4 cells (5 × 10⁴) on day 0. The cause of death was determined by necropsy and is shown in Table 2. Survival is depicted as a Kaplan-Meier curve, and each group contained 10 animals.