Combined cultured allogeneic HSCs with fully mismatched MHC also exhibit beneficial radioprotective and bridging effects. (A) The experimental protocol used to test radioprotective and bridging effects in cultured allogeneic HSCs of strains fully MHC-mismatched to recipients. Three allogeneic strains, DBA/1JJmsSlc (DBA1, H2q, and Ly5.2), DBA/2Cr Slc (DBA2, H2d, and Ly5.2), and C3HHeJ (C3H, H2k, and Ly5.2), were used. HSCs (50 cells) harvested from these allogeneic mice 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 = 0.0013; 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. 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 < 0.01; ***, P < 0.001; ****, P < 0.0001. (D and E) Percentages of donor cell chimerism in granulocytes and BM in individual recipients transplanted with each graft at indicated times after transplantation. n = 7 in each group. Mean values are indicated as bars. D and E represent two independent experimental results. To confirm single-donor chimerism originated from a principal graft (B6-5.1/5.2) at the primitive cell levels in group two, percentages of donor cell chimerism were determined in not only whole cells (WBM) but also a KSL fraction in individual recipients’ BM at 12 wk in E.