Cell dose-dependent engraftment of NOD/SCID mice transplanted with fresh or ex vivo–expanded human CD34⁺ CB cells. The figure represents the proportion of CD45⁺ and double-positive CD45⁺/CD34⁺ cells in the femoral BM of NOD/SCID mice transplanted with 10⁵, 10⁴, and 10³ fresh CD34⁺ CB cells (•) or with the IL-3/IL-6/SCF ex vivo–expanded populations, which corresponded to the incubation of 10⁵, 10⁴, and 10³fresh CD34⁺ cells (○). BM was periodically sampled from day 15 to day 120 posttransplantation. At day 120 posttransplantation, data from spleen (squares), and PB (triangles) are also represented. Samples were ex vivo–expanded with FBS plus IL-3/IL-6/SCF, as indicated in Fig 1.