Engraftment of CB CD34+ cells in NOD/SCID mouse BM is not compromised. CD34+ cells isolated from CB or healthy mPB donors were transplanted into sublethally irradiated (350–375 cGy) NOD/SCID animals or NOD/SCID mice deficient in β2 microglobulin (NOD/SCID-β2mnull). Four weeks after transplantation, mice were sacrificed to assess the levels of human-derived CD45+ cells (a) or colony-forming progenitors (b) in their BM. There is a trend toward higher engraftment of CB-derived CD34+ cells (P = 0.07 for CD45+ and P = 0.1 for CFC content). Each circle in a represents an individual mouse.