Background
Vascularized composite allotransplantation (VCA) has become a valid therapeutic option after devastating tissue loss While costimulation blockade (CoB) has shown considerable efficacy in preventing rejection, its efficacy in VCA remains poorly explored Here we investigated the immunoregulatory potential of CoB in a novel murine model of hind limb transplantation.
Methods
Fully MHC-mismatched allogeneic, orthotopic hind limb transplants were performed from Balb/c to C57BL/6 mice Recipient animals received combinations of total body irradiation (TBI), CTLA4-Ig, and anti-CD154 mAb (CoB) Mixed chimerism, clonal deletion of alloreactive T cells, and cytokine production were assessed by flow cytometry.
Results
CoB treated recipients showed increased survival compared to untreated and CTLA4-Ig only groups (Mean survival time [MST] 82 days) Adding non-myeloablative TBI to CoB enabled indefinite graft survival (MST, >210 days) Mixed chimerism induced by donor- derived bone marrow (BM) was detected in the CoB treated group, and was even higher in TBI+CoB treated recipients Decreased vÎ211+ and vÎ25+CD4+ T cells were detected in both groups treated with either CoB or TBI+CoB, suggesting central thymic deletion of donor reactive T cells Donor specific tolerance was confirmed in long-term survivors (TBI+CoB group) by acceptance of donor matched secondary skin grafts and rejection of third party ones In long term survivors treated with TBI+CoB, decreased T cell responsiveness and increased graft-infiltrating regulatory T cells were detected on POD50.
Conclusion
Our results show that CoB enables the tolerogenicity of BM components carried by VCA, but requires TBI to establish durable donor-specific tolerance.