PU.1-Silenced Dendritic Cells Induce Mixed Chimerism and Alleviate Intestinal Transplant Rejection in Rats via a Th1 to Th2 Shift.

Background/aims: Intestinal transplantation is an effective treatment for end-stage bowel failure; however, graft rejection and the toxicity associated with non-specific immunosuppression are major limitations of this procedure. Studies have shown that mixed chimerism can produce post-transplantation immune tolerance. Here, we demonstrate that in rat intestinal transplantation, PU.1-silenced dendritic cells (DCs) plus bone marrow (BM) cell transfusion results in mixed chimerism, and we investigate the mechanisms responsible for the effects of mixed chimerism rejection.

Methods: In a model of intestinal transplantation, male Brown Norway rats were the donors, and female Lewis rats were the recipients that were randomly divided into 4 groups: control, BM, BM-imDCs and BM-PU.1. The dynamic changes in graft morphology, rejection scoring and serum concentrations of Th1/Th2-related cytokines were investigated on postoperative days 0, 7, 14, 21, and 30.

Results: The BM-PU.1 group had better graft health, milder pathologic injuries, and lower rejection grades compared with the other groups. The rates of mixed chimerism were significantly highest in the BM-PU.1 group and correlated with decreases in serum IL-2 and increases in serum IL-10.

Conclusion: Transfusion of PU.1-silenced DCs and BM cells induces stable mixed chimerism and has the potential to reduce pathologic injuries via a pro-Th2 shift in the Th1/Th2 balance.