Prolonged survival effects induced by immature dendritic cells and regulatory T cells in a rat liver transplantation model.

Background: Dendritic cells (DCs) and regulatory T (Treg) cells are crucial for inducing immune tolerance. However, the suppressive function of infused Treg cells and immature DCs (imDCs) following solid organ transplantation remains unclear.

Methods: ImDCs derived from DA-donor rats and Treg cells isolated from spleens of Lewis rats were prepared. A heterotopic liver transplantation model was established to examine the immune tolerance effects of infusion of Treg-imDCs, imDCs and Treg cells individually. Th1/Th2 cytokines and TRAL were detected by ELISA. The overall rejection grade was assessed and the rejection activity index (RAI) was calculated. TUNEL-positive lymphocytes were detected in the portal area in liver sections.

Results: The infusion of Treg-imDCs was more effective than imDCs or Treg cells individually. Moreover, the expression of IL-10 and TGF-β1 was significantly up-regulated, and IL-12 expression was significantly down-regulated, especially in the Treg-imDCs group. The percentage of TUNEL-positive cells was significantly higher in the Treg cells and imDCs groups. The RAI values in Treg-imDCs group on days 3 and 7 were lower than control, imDCs and Treg cells groups individually (p<0.05). Both TBIL and ALT levels in the Treg-imDCs and imDCs groups were significantly lower than those of the control and Treg cells groups, and serum TRAL levels increased significantly 10days after transplantation in the imDC and Treg-imDC groups compared with the control and Treg cells groups (P<0.001).

Conclusion: These data demonstrated that infusion of Treg cells and/or imDCs induces alloantigen tolerance and prolongs liver allograft survival. The infusion of Treg-imDCs was more effective than imDCs or Treg cells individually. ImDCs synergize with Treg cells in inducing and maintaining the feedback loop between imDCs and Treg cells in vivo.