Prolongation of Composite Tissue Allograft Survival by Immature Recipient Dendritic Cells Pulsed with Donor Antigen and Transient Low-Dose Immunosuppression

BACKGROUND: Composite tissue allograft transplantation is limited by risks of long-term immunosuppression. The authors investigated whether short-term immunosuppression combined with recipient immature dendritic cells pulsed with donor antigens promotes composite tissue allograft survival. METHODS: Orthotopic hind-limb transplants were performed (day 0) from Wistar-Furth (RT1) to Lewis (RT1(u)) rats. Recipient dendritic cells were propagated from bone marrow with granulocyte-macrophage colony-stimulating factor (bone marrow-derived dendritic cells) and pulsed with or without donor splenic cell lysate. Recipients were as follows: group I, control; group II, cyclosporine (10 mg/kg/day, days 0 through 6, intraperitoneally); group III, antilymphocyte serum plus cyclosporine (days -4 and +1, intraperitoneally); and groups IV and V, cyclosporine plus antilymphocyte serum, combined with 7 x 10(6) untreated or donor cell lysate-pulsed bone marrow-derived dendritic cells (days +7 and +14, intravenously), respectively. Epidermolysis/desquamation of donor skin defined rejection. Mixed leukocyte reaction determined recipient T-cell reactivity to donor. Tissue samples were obtained at 3 weeks and on the day of rejection. Groups comprised six or seven rats. RESULTS: Donor alloantigen-pulsed bone marrow-derived dendritic cells (group V) significantly prolonged median composite tissue allograft survival time (32.0 days) compared with groups II (18.0 days, p = 0.0012), III (22.5 days, p = 0.0043), and IV (26.5 days, p = 0.0043). Splenic T cells in group V exhibited hyporesponsiveness to donor alloantigen in mixed leukocyte reaction. Interestingly, the graft muscle component in the bone marrow-derived dendritic cell-treated group (group V) showed significant reduction in mononuclear cell infiltration relative to group II (p = 0.0317). CONCLUSIONS: Donor alloantigen-pulsed recipient bone marrow-derived dendritic cells combined with transient T-cell-directed immunosuppression significantly prolonged composite tissue allograft survival across a full major histocompatibility complex barrier. This may represent the basis for a novel, clinically applicable strategy to promote composite tissue allograft survival with reduced systemic immunosuppression.