Analysis of human engraftment and frequency of primitive human FB cells capable of repopulating NOD/SCID mice.
(A) Representative Southern blot analysis of liver, lung, muscle, spleen, kidney, and BM of 2 individual NOD/SCID mice transplanted with 4 × 105 human FB-MNCs. DNA was extracted from murine BM 8 weeks posttransplantation and hybridized with a human chromosome 17–specific α-satellite probe. Human cells were detectable in the BM of mouse FB12.8 by flow cytometric analysis using the human-specific panleukocyte marker CD45, whereas no human CD45+ cells were detectable in the BM of mouse FB12.9. (B) Representative Southern blot analysis of 9 individual NOD/SCID mice transplanted with a single FB sample using 8 × 105 (lanes 1-3), 4 × 105(lanes 4-6), and 2 × 105 FB-MNCs (lanes 7-10). (C) Summary of the level of human cell engraftment in the BM of mice transplanted with human FB-MNCs from 6 independent samples. NOD/SCID mice (n = 27) were transplanted with various doses of FB cells (range, 1 × 105 to 1 × 106). Each symbol represents a single NOD/SCID recipient. Mice were considered to be engrafted if a band was detectable by Southern blotting of the extracted DNA followed by hybridization with a human-specific probe (limit of detection of 0.05% human). Poisson statistics were applied to the single-hit model, and the frequency of SRCs, calculated using the maximum likelihood estimator, was 1 SRC in 3.2 × 105FB-MNCs (95% confidence interval, 1 in 1.8 × 105 to 1 in 7.2 × 105).
