Secondary engraftment of tissues expressing EGFP transgene in the absence of DBY antigen. (A) A total of 7 × 10⁶ male 45.2 BM cells from transgenic EGFP mice were transferred into 45.2 male hosts, 45.2 female hosts, or 45.2 female hosts conditioned with 10⁵ DBY-Tregs. One representative FACS analysis of 3 experiments is shown (day 150). (B) Donor chimerism expressed as a percentage of EGFP-positive cells analyzed in PBMCs 5 months after EGFP BM transfer as in panel A. Results represent the mean of 3 mice per group ± SEM. (C-D) BM from EGFP × CD45.1 male or female mice was transferred into 45.2 EGFP chimeric or naive female mice. Representative FACS analysis (C) and percentage of EGFP^high and CD45.1⁺ cells (D) in PBMCs at 5 months are shown. Results represent the mean of 3 mice per group ± SEM. Statistical analysis was performed using the Mann-Whitney t test; *P ≤ .05. (E) Long-term engraftment of EGFP female skin grafts in EGFP male-female chimeric mice (n = 8, ▪). In the controls, 5 of 6 chimeric mice lacking EGFP (♦) and 4 of 4 female B6 mice (▴) rejected the EGFP female skin graft between day 12 and day 16. The results presented are pooled from 2 independent experiments.