Repopulation of NOD/SCID mice. (A) Human CD34⁺ UCB cells efficiently repopulate BM of NOD/SCID mice. (Left) Expression of human CD45 within the lympho/monogate. (Right) Expression of CD19 and CD14 within the CD45 gate. (B) No human CD45⁺ cells were detected in BM of mice that received a transplant with CD34⁺CD1a^– thymocytes (left) or with CD34⁺CD1a⁺ thymocytes (right).