Analysis of engraftment of human cells in NOD/SCID mice by FISH. (A) Human cells detected by D8Z2 probe show two bright green fluorescent signals in contrast to murine cells with no signal (original magnification × 200). (B) Differential engraftment of normal and leukemic CML cells in NOD/SCID mice detected by dual probes for bcr and abl. Normal cells show two red ablsignals and two green bcr signals. Leukemic cells show a single red and green signal representing normal abl and bcrgenes and the yellow signal representing fusion of abl andbcr genes (original magnification × 1,000).