Development of human CD34⁺ cells in the hematopoietic tissues of NOD/SCID mice. (A) Typical profiles of human progenitor cell (CD34, CD33), myeloid cell (CD13, CD14), B-cell (CD19), and T-cell (CD2) surface markers on huCD45⁺ output cells from the BM, spleen, and PB of repopulated mice. Cells in the glycophorin A⁺ gate were 100% huCD71⁺ and 0% to 3% huCD45⁺. Quantification of the CD34⁺ population was done by using a four parameter gating method.31 (B) In the rare cases where huCD45⁺ cells populated the thymus (two mice), the vast majority (98%) were huCD2⁺ (upper histogram). When the thymic population was gated on huCD3⁺ cells (which comprised 72% of the total cells), 95% were hu CD4/CD8 double positive cells (lower histogram).