Detection by flow cytometry of human CD34⁺Thy-1⁺ cells in the BM of transplanted mice. Analysis of a representative mouse (18.1) transplanted with 10⁸ BM cells from patient 10 and killed 1 month later. (A) Histogram showing the proportion of viable (PI⁻) human (CD45/71)⁺ cells present in the BM of this mouse. (B) and (C) Percentage of CD34⁺ and CD34⁺Thy-1⁺ cells determined by staining with human-specific anti-CD34–FITC and anti-Thy-1–phycoerythrin antibodies. Gates defining positive cells were set to exclude greater than 99.9% of cells stained with monoclonal antibodies of the same isotype and labeled with the corresponding fluorochromes.18 23