Chronic immunosuppression is essential for maintaining human hand transplant survival because composite tissue allografts are as susceptible to rejection as visceral organ allografts. Limb allografts comprise different types of tissues with varying antigenicities, and the immuno-suppressive doses required for these allografts are as high or higher than those required for solid organ allotransplantation. In particular, bone marrow is an early target of the host immune response. This study reports on donor limb modification of the marrow compartment leading to prolonged survival of limb allografts. Chimeric limb allografts comprising a Lewis rat vascularized allograft and Brown Norway rat bone marrow were created. These chimeric limbs were transplanted into three recipients: (1) Buffalo rats (n=12), where the chimeric limb was allogeneic for both vascular graft and bone marrow; (2) Lewis rats (n=12), where the limb was allogeneic for marrow alone; and (3) Brown Norway rats (n=12), where the limb was allogeneic for graft alone. This study found that Brown Norway recipients elicited significantly reduced cell-mediated and humoral immune responses in comparison with the Buffalo and Lewis recipients (p<0.001 and p<0.01, respectively), The Buffalo and Lewis recipients both elicited high cell-mediated and humoral responses. The Brown Norway recipients also had prolonged survival of limb tissue allograft in comparison with the other experimental groups.
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