CRA of the hematopoietic lineages by WT andPU.1^−/− E14.5 FL cells. Irradiated Ly 5.1 adult mice (Hbb^s) were transplanted with either 70% (5 × 10⁵), 80% (1 × 10⁶), or 90% (2 × 10⁶) E14.5 FL progenitors from donor WT (PU.1^+/+,/−) orPU.1^−/− embryonic littermates (Ly 5.2, Hbb^d). A radioprotective dose of 2 × 10⁵normal adult bone marrow cells was included as a source of competitive, syngeneic HPC. Peripheral blood was taken from recipient animals on a monthly basis for 6 months postengraftment. (A) Contribution of donor HPC to peripheral blood erythrocytes. Cellulose acetate electrophoreisis was used to separate donor from recipient hemoglobin isoforms. Relative contribution was determined by scanning densitometry and expressed as the percentage of donor contribution to total hemoglobin production. Data from 3 independent experiments are depicted on the graph. Solid lines represent animals that received WT donor HPC. Dashed lines represent animals that receivedPU.1^−/− donor HPC. (B) Contribution of donor HPC to the lymphoid and myeloid lineages. Contribution to the lymphoid and myeloid lineages was determined by flow cytrometric analysis using an Ly 5.2-specific MoAb to identify donor-derived cells and lineage-specific MoAbs to characterize the B-cell (B220⁺), T-cell (CD4⁺), and monocyte (CD11b⁺) populations. Representative FACS profiles are shown for peripheral blood samples obtained at 2 months posttransplantation for lethally irradiated Ly 5.1⁺ adult mice receiving either pooled WT or PU.1^−/−E14.5 FL HPC (Ly 5.2⁺).