Comparison of adult pre-B ALL engraftment by either unconditioned (−TBI) or 2.5-Gy TBI preconditioned (+TBI) xenotransplant assaying. (A) Comparison of percentage of engraftment in 8 samples assayed by ±TBI following IV transplantation. Symbols correspond to a single mouse. (B) Engraftment kinetics of 2 non-t(4;11) pre-B ALL samples by IBM alone, IBM injection + TBI, and IV injection + TBI. Mean leukemia engraftment (CD45⁺/CD19⁺) ± standard error of the mean (SEM) are shown at the indicated time points as ascertained by IBM sampling (first time point sampled from noninjected bone). More than 2 mice injected per condition. ***P < .0001 compared with IBM and IV + TBI. *P < .05 compared with IBM and IV + TBI.