Morphologic analysis of murine BM and spleen engrafted with CML cells. (A) Histologic section of tibia of NOD/SCID mouse irradiated but not infused with human cells at day 62 (original magnification × 400). (B) Histologic section of tibia of mouse with human cells detectable at day 62. Hypercellular marrow with proliferation of megakaryocytes is shown (original magnification × 400). (C) Histologic section of spleen from control mouse showing monomorphic lymphoid population (original magnification × 400). (D) Histologic section of spleen of mouse with human cells detectable at day 62. Infiltration with megakaryocytes is shown (original magnification, ×400). (E) Cytospin preparation of bone marrow from control mouse (original magnification × 400). (F) Cytospin preparation of bone marrow of mouse with human cells detected at day 62 showing prominent myeloid cells (original magnification × 400). (G) Cells detected by FISH with dual probes for bcr and abl showing no signal in cells from the bone marrow of control mouse (original magnification × 1000). (H) Differential engraftment of normal and leukemic CML cells in NOD/SCID mice detected by dual probes for bcr and abl genes. Normal cells show 2 red abl signals and 2 green bcr signals. Leukemic cells show a single red and green signal representing normal abl and bcr genes and the yellow signal representing fusion of abl and bcr genes (original magnification × 1000). The magnifications/numerical apertures of the objective lenses used were as follows: for panels A-F, 40×/0.65; for panels G-H, 100×/1.25.