Higher levels of human cell engraftment in NOD/SCID/B2m^null mice.

(A) Summary of engraftment levels in mice transplanted with enriched cord blood CD34⁺ cells. Similar percentage of human engraftment was detected by either Southern blot with human-specific α satellite probe (open circles) or by flow cytometry using human-specific anti CD45 mAb (filled circles). NOD/SCID mice were transplanted with 8 × 10⁴ cells per mouse and NOD/SCID/B2m^null mice with 4 × 10⁴ cells per mouse, in 5 independent experiments. (B) Bone marrow cells of mice presented in A were assayed for colony formation in semisolid culture selective for the growth of human colonies. Data shown are mean ± SE of 5 experiments. (C) Human DNA in the bone marrow of primary NOD/SCID/B2m^nullmice transplanted with 10³ CD34⁺ cells (lanes 1-3) and NOD/SCID mice transplanted with 10⁴CD34⁺ cells (lanes 4-6). Secondary NOD/SCID/B2m^null recipients were transplanted with 2 to 5 × 10³ human CD34⁺ cells that were recovered from engrafted primary NOD/SCID mice (lanes 7, 8). (D) NOD/SCID mice were transplanted with 12.5 × 104cord blood MNC per mouse (DI) and NOD/SCID/B2m^null mice with 8 × 104or 5 × 10⁴ cord blood MNC per mouse (DII and DVI, respectively). Bone marrow cells from transplanted mice were analyzed 1 month later for the presence of human CD45⁺cells (R2). Human lineage-specific mAb were used to detect lymphoid CD45⁺CD19⁺ (DII, DVI, R1), myeloid CD45⁺CD33⁺ (DIII), and immature CD34⁺CD38^−/low (DIV) progenitor cells in the marrow of engrafted NOD/SCID/B2m^null mice. Lymphoid CD45⁺CD56⁺ NK cell differentiation was induced in vitro before analysis (DV). A representative mouse out of 9 in 3 different experiments is shown.