Kinetic analysis of T-ALL engraftment after serial transplants. Blast cells from the spleen or bone marrow of secondary and tertiary engrafted mice were transplanted (250 000 cells/mouse) in the femur of recipient mice. CD45⁺ engraftment levels were measured over time in (A) the IBM and in (B) the spleen and noninjected bones (NIBM, right panel) of NOD-Scid recipients. *P < .05; **P < .01; ***P < .001; NS, not significant. (C) Limiting dilution experiment performed with M30 T-ALL. Cells were transplanted into mice and engraftment levels were tested in IBM, NIBM, and spleen 2 months after transplantation. Positivity was established when more than or equal to 0.1% human CD45⁺ cells were detected.