Combined cultured F1 HSCs support early hematopoiesis, while allowing single-donor chimerism from a congenic graft. (A) The experimental protocol to test cultured allogeneic HSCs for their radioprotective and bridging effects in a transplantation model. HSCs (50 cells) harvested from the four allogeneic mouse strains indicated were cultured for 7 d, combined, and transplanted together with uncultured WBM cells derived from B6 (Ly5.1/5.2) into lethally irradiated B6 (Ly5.2) recipients. (B) Kaplan-Meier plot showing survival among mice transplanted with indicated grafts. Allogeneic HSCs, Allo-HSCs. n = 7 in each group. Log-rank testing was used to analyze survival data. P = 0.0066. P < 0.025, Bonferroni-corrected threshold, was considered statistically significant. *, P < indicated Bonferroni-corrected threshold. (C) Results of complete blood counts in PB, WBC (left), hemoglobin (middle), and platelets (right), from recipients transplanted with each indicated graft (same experiment as Fig. 6 B). n = 7 in each group. One-way ANOVA with Tukey’s multiple comparison test was used for statistical analysis. Mean values are indicated as bars. P < 0.05 was considered statistically significant. *, P < 0.05; **, P < 0 0.01; ***, P < 0.001; ****, P < 0.0001. (D) Percentages of donor-cell chimerism in granulocytes and BM in individual recipients transplanted with each indicated graft at indicated times after transplantation. n = 7 in each group. Mean values are indicated as bars. (E) Percentages of %KuO⁺ cells (B6C3F1 donor) in platelets (left) and red blood cells (right) in individual recipients. Mean values are indicated as bars. n = 7 in each group. Representative data are shown from at least two independent experiments for each panel.