Only SP cells within the KSL population contain LT-HSCs. (A) Whole bone marrow was stained with antibodies against c-Kit, Sca-1, and lineages. The KSL population represented approximately 0.1% of nucleated cells. Right panel shows Hoechst profile of KSL-gated cells. Approximately 25% to 35% of cells fell into the SP gate. Regions marked as SP and non-SP (nSP) were sorted and then re-sorted for transplantation experiments. (B) Reconstitution profiles of mice that received transplants of limited cell numbers of KSL-SP or KSL non-SP cells along with a radioprotective dose of 1 × 10⁵ host-type whole bone marrow cells. Peripheral blood chimerism is shown at 1 month (•), or 6 months (○) after transplantation.