Combined treatment with regulatory T cells and vascularized bone marrow transplantation creates mixed chimerism and induces donor-specific tolerance to vascularized composite allografts without cytoreductive conditioning

We demonstrate herein that combination treatment with regulatory T cells (T_regs) and vascularized bone marrow transplantation (VBMT) can achieve stable mixed chimerism and long-term transplantation tolerance to vascularized composite allografts (VCA) without requiring cytoreductive recipient conditioning in rats. An appreciable number of T_regs of recipient origin was shown at the interface between recipient and transplanted VCA tissues, implicating a significant role for T_regs in protecting VCA from rejection. This cytoreduction-free protocol using co-treatment with T_regs and VBMT warrants further investigation toward potential clinical application for VCA transplantation.