Engraftment of FR25Lin⁻ or R/O cells into secondary recipients of PKH⁺ cells. One hundred PKH bright BM cells recovered 48 hours posttransplant from male FR25Lin⁻ donors (•) or male R/O donors (∗) were injected into secondary female hosts. Peripheral blood was obtained from these recipients at 6, 12, and 24 weeks posttransplant and analyzed for the presence of male cells. Values represent the mean percent male cells for 4 to 6 recipients. The mean survival for secondary recipients receiving R/O PKH⁺ cells was 12.1 ± 5.4 weeks.