Production of B-cell, T-cell, and myeloid lineages by donor-marked KTLS cells isolated from BM of HU-treated mice. KTLS cells and subsets of KTLS cells were isolated from mice treated with HU (100 mg/kg/d) for 3 days. Host mice were lethally irradiated and reconstituted with 10⁵ recipient-type BM cells and 10 KTLS cells (top FACS plots) or 10 S/G2/M Rh123^mid KTLS cells (bottom FACS plots). Cells that arise from donor KTLS expressed a donor-specific Ly-5 allele. Six months later, peripheral blood was obtained and analyzed for donor-specific myeloid lineages (Mac-1 and Gr-1), B cells (B220), or T cells (CD3). The percentage of a lineage-specific Ly-5⁺ population that originated from donor KTLS cells is indicated in the upper right corner of each plot. Anti-B220 staining was suboptimal in 1 experiment (e) compared with the typical staining profile (b). The percent of donor-type B cells (B220, ▴), T cells (CD3, ♦), and myeloid cells (Mac-1 and Gr-1, •) in the peripheral blood was assessed monthly for 6 months. Two examples of multilineage reconstitution with 10 Ly-5–marked KTLS cells are shown: (g) an example of the long-term production of B cells, T cells, and myeloid cells, and (h) an example of multilineage reconstitution with transient myelopoiesis. Myeloid cells have a short life span and therefore are a good indicator of continuous hematopoiesis originating from donor HSCs.