Ph⁺ ALL growth in vivo is inhibited by CR4. NOD-SCID mice were injected with Ph⁺ ALL (Z119) cells as described in “Materials and methods” and treated with CR4 or solvent (DMSO/PBS) delivered by osmotic pump. (A) After 14 days of treatment, mice were killed and single-cell suspensions prepared from bone marrow. After red cell lysis, the samples were stained with human-specific anti-CD19 (and isotype control) to detect infiltrating ALL cells. Anti-CD19 does not cross-react with murine cells. Similar results were obtained by staining with anti-HLA-DR. (B) To assess the viability of infiltrating Z119 cells, bone marrow cells were also cultured in colony-forming assays. BM cells were cultured in semisolid medium supplemented with 30% serum (1:1, bovine FCS-human plasma), but without addition of exogenous cytokines. There is no growth of murine cells under these conditions. The number of ALL colonies was evaluated after 9 days of culture. Shown is one of 2 experiments with standard deviations.