Anatomic distribution of human cell engraftment. Mice receiving transplants of CD34⁺ and CD34⁺CD38^- cells were scanned 9 weeks after transplantation (A) and then killed. Bone marrow cells were harvested from each region of the skeleton and analyzed by FACS for percentage (B) and total number (C) of donor human CD45⁺ cells. Scap indicates scapula; ▪, CD34⁺; and □, CD34⁺CD38^-.