INDUCTION OF DONOR-SPECIFIC T CELL HYPORESPONSIVENESS BY RECIPIENT-DERIVED ENDRITIC CELLS

Abstract

O262* Aims: Administration of donor-derived immature dendritic cells (DC) treated with NF-κB oligodeoxyribonucleotides (ODN) prevents allograft rejection. This DC vaccine regimen is however, not applicable for clinical employment, as cadaveric organ transplantation is a semi-emergency surgery, while DC propagation requires at least 5-6 days. We attempted to explore the use of recipient-derived DC pulsed with donor antigens, in which the donor antigens were presented to host T cells via indirect pathway (cross-priming). Methods and Results: DC were propagated from C3H (H-2k) bone marrow (BM) with GM-CSF and IL-4. 10 mM NF-κB ODN were added at the initiation of culture (NF-κB ODN DC), and pulsed with B10 (H-2b) splenocyte lysate at 1/5 DC/splenocyte ratio for the last 48 h of the culture. DC surface molecule expression was examined by flow cytometry. Their allostimulatory activity was assessed in vitro by MLR, and in vivo by the influence on B10 cardiac allograft survival. Cytokine profiles were analyzed by ELISA and RNase protection assay. NF-κB activity in DC nuclear protein was detected by gel shifting assay. Expression of CD40, CD80 and CD86 on DC was significantly inhibited by treatment with NF-κB ODN, while MHC class I and II was minimally affected. Normal C3H DC pulsed with B10 antigens stimulated prolifereative responses and donor-specific CTL activity in C3H T cells, both of which were however, markedly inhibited when DC were treated with NF-κB ODN. This was associated with reduced IFN-γ and increased IL-10 production in the supernatant, suggesting a Th2 bias. Apoptotic T cells were observed to be more frequently in cultures with NF-κB ODN DC. In contrast to administration of normal DC pulsed with donor antigens that accelerated rejection of B10 cardiac allografts (median survival time [MST] 7 days vs 10 days in no-DC treatment control, p<0.05), a single injection of 2 x 106 NF-κB ODN DC significantly prolonged allograft survival (MST 50 days, p<0.05 compared with no-DC treatment control). Conclusion: These data indicate that vaccination with immature DC propagated from recipient BM is an more feasible approach to induce T cell hyporesponsiveness.