ABSTRACT
BACKGROUND: Tolerance is more easily induced in liver transplant models than in other organs; CD8+CD45RClowregulatory T cells (Tregs) have been shown to induce tolerance in heart allografts. Whether CD8+CD45RClowTregs could induce tolerance in a liver transplant model and how dendritic cells (DCs) mediate the CD8+CD45RClowTregs effect remains to be investigated. METHODS: A rat liver transplantation model was established and used to test tolerance and acute rejection compared to control groups. Liver function and histopathological changes of allograft were examined by enzyme-linked immunosorbent assay (ELISA) and haematoxylin and eosin (H&E) staining, respectively. The distribution and proportion of CD8+CD45RClowTregs and plasmacytoid dendritic cells (pDCs) in the allografts and spleen were determined using flow cytometry. Cytokine secretion levels were determined using ELISA and real-time quantitative PCR (qRT-PCR). RESULTS: The rat liver transplantation model was well established, with a success rate of 93.3% (28/30). The mean survival time of the tolerant and acute-rejection rats were 156 and 14 days, respectively. The proportions of CD8+CD45RClowTegs were higher in the allografts of tolerant rats than in those of acute-rejection rats (33.1 ± 4.3 and 12.4 ± 4.6, respectively; P = 0.04). Significant accumulation of pDCs was observed in tolerant liver graft rats compared to that in acute-rejection rats (1.46 ± 0.23 and 0.80 ± 0.20, respectively; P = 0.02). Importantly, CD8+CD45RClowTregs were positively associated with the frequency of pDCs (P = 0.001, r2 = 0.775). The protein and mRNA expression of IL-10 and TGF-ß in the allograft group were increased, possibly being responsible for tolerance induction. CONCLUSION: CD8+CD45RClowT cells interact with pDCs through the induction of IL-10 and TGF-ß expression and are responsible for inducing immune tolerance in rat liver transplantation.