Human engraftment 12 weeks after transplantation. B-lymphoid–restricted engraftment of human lin^– CD3^– SP mPB cells (A) and myeloid-lymphoid engraftment of human lin^– CD3^– non-SP mPB cells (B). FACS analysis of bone marrow cells of mice 12 weeks after transplantation. Cells were stained with anti–human CD45/71-PE, CD15/66b-FITC, CD56-PE, CD3-FITC, CD19/20-PE, CD34-FITC, and CD33-PE. B-lymphoid cells were detected in 4 of 19 mice after transplantation of 300 to 3000 lin^– CD3^– SP mPB cells in 3 independent experiments.