Percentage of donor (Ly-5.1) cells in the blood of individual secondary recipients. Ly-5.1 Lin⁻c-kit⁺ Sca-1⁺ CD34⁺post–5-FU marrow cells were transplanted to Ly-5.2 primary recipients. Three months later, 1,000 Ly-5.1 CD34⁻ bone marrow cells or 5,000 Ly-5.1 CD34⁺ bone marrow cells of the primary recipients were transplanted to individual secondary Ly-5.2 recipients. (○) 2 months posttransplantation; (•) 5 months posttransplantation.