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Background: Immunological status is still one of the key points discussed in the area of composite tissue allotransplantation (CTA) mainly due to the risks of life-long systemic immunosuppression. This study focus on immature dendritic cells (imDCs) and CD4+CD25+Foxp3+ regulatory T cells (Treg) to find their immunoregulatory roles in CTA, and meanwhile to find a mild immunoregulation way with minimal drug side-effects. Methods: Superficial inferior epigastric artery flap fromBrown-Norway (RT1n) was transplanted to Lewis (RT11) rats (day 0). ImDCs were propagated from the recipient (Lewis, RT11) or donor (Brown-Norway, RT1n) bone marrow, stained with CFSE and then topically transfused into allografts through femoral artery pedicle on day 0. Group 1 (control group) did not receive any treatment. Groups 2 received rapamycin (Rapa) at a concentration of 2mg/kg/day on days 0-7 postoperative. Groups 3 received donor imDCs transfusion. Groups 4 received recipient imDCs transfusion. Group 5 received combined treatment with donor imDCs and Rapa (2mg/kg/day, days 0-7). Group 6 received combined treatment with recipient imDCs and Rapa (2mg/kg/day, days 0-7). Graft rejection was defined as epidermolysis/ desquamation/gangrene of the donor skin. Tissue samples were biopsied to analyze the histological changes, and flow cytometry was performed to trace the location of imDCs labeling with CFSE and to quantify the recipient Treg on endpoint of rejection.

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