Prolonged Survival of Vascularized Skin Grafts Across a Full MHC Mismatch Using Donor Antigen-Pulsed Tolerogenic GM+Rapa Dendritic Cells (102.22)

Abstract We compared the tolerogeneic properties of BM-derived GM+IL-4 and GM+Rapa host DCs and their potential to induce long-term acceptance of vascularized skin allograft in rats across a full MHC mismatch with transient immunosuppression. Results show that both DCs were CD11b+ and expressed low levels of CD86 and produced low levels of IL-12p70 following TLR activation. GM+Rapa DC produced lower levels of anti- and pro-inflammatory cytokines in response to LPS. Both DCs had low T cell stimulatory capacity in vitro. Interestingly, donor Ag-pulsed GM+Rapa DC (GM+Rapa DCp) induced long-term survival of the vascularized skin grafts and this was significant compare to GM+IL-4 DC and control groups. PBMC from long-term graft survivors that were previously treated with donor Ag-pulsed GM+Rapa DC were hyporesponsive to donor Ag, but proliferated in response to the third-party Ag and produced IL-10 in addition to IFN-gamma. Recipients of the long-term surviving allografts were challenged with full-thickness tail skin grafts. While the third-party grafts were rejected fast the donor graft had delayed rejection, suggesting that this treatment induced a regulatory mechanism that prevented the acute rejection of donor skin grafts. Further experiments demonstrated presence of CD4+ Foxp3+ T cells in the vascularized skin and secondary lymphoid tissues. Taken together, these results demonstrate that the donor Ag-pulsed tolerogenic GM+Rapa DC have ability to induce regulatory T cells and prevent vascularized skin graft rejection across a full MHC mismatch.