Anti–third-party Tcms mediated chimerism specifically protects donor skin graft from rejection. Sublethally irradiated (5.5Gy/4.5Gy TBI) Balb/c (H-2^d) mice were transplanted with 20 × 10⁶ C57BL/6-nude (H-2^b) BM cells with or without administration of 5 × 10⁶ C57BL/6 Tcm. The indicated groups received subcutaneous injections of 0.5 mg/kg rapamycin during 5 days (days −1 to +4). On day 30 after BM transplantation skin grafting of donor-type (C57BL/6, H-2^b) as well as third-party (C3H, H-2^k) was carried out (each recipient was transplanted with both grafts). Recipients of skin grafts were either BM control mice (“5.5Gy+BM” and “4.5+BM” Groups) which had rejected the donor-BM or those Tcm-treated mice which had achieved donor-chimerism. (A) Representative images of skin grafts across experimental groups taken 4 months after skin grafting. (B) Bars show percentage of chimeras that accepted donor skin grafts across experimental groups during a > 4-month follow-up period after skin grafting. Data were pooled from 6 independent experiments (***P < .001 by X²).