Flow cytometric detection of fetal liver donor–derived cells after reconstitution in SCID-hu mice. (A) BM cells recovered 8 weeks after injection. HLA-A2 positive, fetal liver donor–derived cells are identified in the HLA expressing human cell population (top left), CD19⁺ B cells (top right), CD33⁺ myeloid cells (bottom left), and CD34⁺ progenitor cells (bottom right). A smaller population of HLA-A2 negative, bone donor–derived cells is found in each population. (B) Thymocytes recovered 12 weeks after injection. HLA-A2 positive, fetal liver donor–derived cells can be clearly detected in the CD3^high population (upper right quadrant) in the reconstituted thymus (right) but not in the uninjected thymus (left).