A modified multiple-donor transplantation model using combined allografts yields single-donor chimerism with beneficial radioprotective and bridging effects. (A) Cell dose titration by survival assay in congenic mouse transplantation conducted as shown in Fig. 1 A. Whole BM (WBM) cells were used instead of KSL cells as test cells. n = 5 in each group. P = 0.0031; P < 0.01, Bonferroni-corrected threshold, was considered statistically significant. *, P < indicated Bonferroni-corrected threshold. (B) The experimental protocol for testing radioprotective and bridging effects in combined allogeneic KSL cells in a modified model. In brief, B6-Ly5.1 KSL cells shown in Fig. 1 C are replaced by B6-Ly5.1 WBM cells. 500 KSL cells from allogeneic strains and 5 × 10⁴ congenic WBM cells are used. (C) Kaplan-Meier plot showing survival among mice receiving indicated grafts. Allogeneic-KSL, Allo-KSL. n = 6 in each group. Log-rank testing was used to analyze survival data. P = 0.0039. P < 0.016, Bonferroni-corrected threshold, was considered statistically significant. *, P < indicated Bonferroni-corrected threshold. (D) Percentages of peripheral donor-granulocyte chimerism in individual recipients transplanted with congenic grafts (left) and combined allogeneic grafts (right) as a supportive unit. n = 6 in each group. Mean values are indicated as bars. (E) Results of complete blood counts in PB from recipients transplanted with congenic grafts alone (purple and green) or mixed allogeneic grafts in addition to congenic WBM (blue). Values in dead mice were regarded as 0 for the analysis. One-way ANOVA with Tukey’s multiple comparison test was used for statistical analysis. n = 6 in each group. Mean values are indicated as bars. P < 0.05 was considered statistically significant. *, P < 0 0.05; **, P < 0 0.01. Representative data are shown from at least two independent experiments for each panel.