Quantitative analysis of SRC after 3 or 6 days of ex vivo cultures. Southern blot analysis of DNA extracted from the BM of individual NOD/SCID mice transplanted with 10⁵CD34⁺ uncultured cells or with their expanded progeny after ex vivo cultures. (A) Representative Southern blots. BM of mice transplanted with human BM CD34⁺ cells cultured for 3 days with indicated cytokine combinations. BM of mice transplanted with the original CB CD34⁺ cells before seeding (day 0) or with cells expanded ex vivo for 6 days with SCF + FL + IL6RIL6 chimera. DNA was extracted from the BM of transplanted mice 1 month after transplantation and was hybridized with a human-specific probe. (B) A summary of the levels of human cell engraftment by percentage of human DNA in the BM of mice transplanted with ex vivo-cultured CB and BM CD34⁺ cells. Cells were cultured for 3 or 6 days before transplantation with the cytokine combinations as indicated. Values shown are the mean ± SE from 7 independent experiments, with an average of 7 mice per group. The differences between SCF + FL + IL6RIL6 chimera and other combinations or noncultured day 0 cells for both time points were significant (P = .0002).