MEC1 cells injected intravenously localize in several organs of Rag2^−/−γ_c^−/− mice. MEC1 cells expressing GFP (A) were injected intravenously into Rag2^−/−γ_c^−/− male mice (n = 3) and killed 2 weeks after injection. Cells collected from spleen (B), peripheral blood (C), bone marrow (D), and peritoneal cavity (E) were analyzed by flow cytometry after staining with mAb against human CD19 to identify the GFP⁺ leukemic B-cell population.