Eμ-myc/bcl-x^−/− fetal liver cells engraft and restore hematopoiesis in lethally irradiated recipient mice. (A) Generation of mice reconstituted with an Eμ-myc/bcl-x^−/− (Ly5.2⁺) hematopoietic system. Fetal liver cell (FLC) suspensions were prepared from Eμ-myc/bcl-x^−/− or, as controls, Eμ-myc, bcl-x^−/− or non-transgenic wt E12.5 embryos (all C57BL/6-Ly5.2). The FLC (2 × 10⁶) were combined with ∼ 1 × 10⁵ bone marrow cells from rag-2^−/− (C57BL/6-Ly5.1) mice and injected intravenously into lethally irradiated C57BL/6-Ly5.1 recipient mice. (B) Functional erythropoiesis in lethally irradiated mice coreconstituted with Eμ-myc/bcl-x^−/− fetal liver cells plus rag-2^−/− bone marrow leukocytes. Peripheral blood was harvested from reconstituted mice generated as shown in panel A and subjected to automated analysis (Advia 120; Bayer). Data shown demonstrate that (left panel) red blood cell numbers (× 10⁹/mL), (middle panel) hematocrit (%) and (right panel) hemoglobin content (g/dL) were all within the normal range (normal ranges for these parameters for un-manipulated, adult C57BL/6 mice are indicated by brackets on the right side of the graphs). Data represent means ± SEM from 6-12 recipient mice transplanted with fetal liver cells of each genotype and were derived from at least 3 separate sets of analyses. (C) Peripheral blood leukocytes from reconstituted animals (generated as described in panel A) were stained with fluorochrome-conjugated monoclonal antibodies to Ly5.1, Ly5.2, B220, IgM and IgD and analyzed by flow cytometry. Representative FACS profiles demonstrate the relative frequencies of fetal liver donor-derived (gated on Ly5.2⁺) B lymphoid cells (B220⁺sIg⁺) in peripheral blood of mice reconstituted with fetal liver cells of the indicated genotypes. A summary of such data from analysis of bloods from multiple animals of each genotype is shown in Figure 3B.