Limiting dilution assay
| Transplanted MNC (cells/mouse) . | No. engrafted mice . | No. transplanted mice . |
|---|---|---|
| 1.25 × 104 | 0 | 5 |
| 2.5 × 104 | 2 | 5 |
| 5.0 × 104 | 5 | 6 |
| 1 × 105 | 8 | 8 |
| 2.5 × 105 | 5 | 5 |
| Transplanted MNC (cells/mouse) . | No. engrafted mice . | No. transplanted mice . |
|---|---|---|
| 1.25 × 104 | 0 | 5 |
| 2.5 × 104 | 2 | 5 |
| 5.0 × 104 | 5 | 6 |
| 1 × 105 | 8 | 8 |
| 2.5 × 105 | 5 | 5 |
NOD/SCID/B2mnull mice were irradiated with 350 cGy and transplanted with 1.25 × 104 to 2.5 × 105 cord blood MNC per mouse, a range that includes cell doses that do not engraft all injected mice. Mice were scored positive if ≥0.1% human DNA was detected by Southern blot analysis in the murine bone marrow. The frequency of engrafting cells in cord blood MNC cells transplanted into NOD/SCID/B2mnull mice was found to be 1 in 3.6 × 104 MNC (95% confidence limits − 1 in 2 × 104 to 1 in 6.3 × 104). Data were analyzed by applying Poisson statistics to the single-hit model, and the frequency was calculated using the maximum likelihood estimator.22