Objective To investigate the mechanism of immune hyporesponsiveness induced by donor-antigen- unloaded recipient-derived immature dendritic cell (imDC) of liver grafts in rats. Methods Forty Sprague-Dawley rats (donor) and forty male Wistar rats (recipient) were randomly divided into 4 groups: control

cyclosporine A (CsA)

mature DC (mDC)

and imDC groups respectively

with 10 donor rats and 10 recipient rats in each group. Recipient rats in CsA group were treated with 10 mg•kg-1•d-1 CsA starting day 2 after the transplantation. Recipients in the mDC or imDC groups were given Wistar rat derived mDCs (1×106/rat) or imDCs (1×106/rat) via dorsal vein of the penis respectively 1 day before the transplantation. In each group

5 recipients were kept for determination of survival time and the other 5 rats were executed at day 10 after transplantation. Blood samples were collected for the measurement of serum alanine aminotransferase (ALT)

total bilirubin (TBIL)

interleukin 2 (IL-2)

interferon gamma (IFN-γ)

IL-4

and IL-10 levels. Liver tissue was harvested for HE staining and acute rejection evaluation. Expression levels of Fas-L/Fas in the grafts were detected by immunohistochemical staining; and Western blot was used to detect the expression level of Scurfin. Results The survival time of CsA and imDC groups was significantly longer than that of control and mDC groups (all P<0.05). The levels of serum ALT and TBIL in the control group (2072.20±217.93 IU/L and 147.42±22.02 µmol/L) and mDC group (2117.00±285.13 IU/L and 141.58±20.82 µmol/L) were significantly higher than those in the CsA group (59.68±13.48 IU/L and 15.40±2.13 µmol/L) or imDC group (50.80±9.63 IU/L and 14.44±3.49 µmol/L) (all P<0.05). In the CsA and imDC groups

the levels of IL-2 (22.52±3.75 pg/mL and 22.12±3.90 pg/mL) and IFN-γ (309.20±25.19 pg/mL and 321.00±21.64 pg/mL) were significantly lower

but the levels of IL-4 (297.60±25.07 pg/mL and 277.00±22.47 pg/mL) and IL-10 (1226.00±140.49 pg/mL and 1423.00±106.39 pg/mL) were higher than those of the control (IL-2: 147.78±12.80 pg/mL

IFN-γ: 1758.60±106.22 pg/mL

IL-4: 17.40±4.77 pg/mL

IL-10: 81.00± 9.47 pg/mL) and mDC groups (IL-2: 142.34±9.29 pg/mL

IFN-γ: 1835.00±82.63 pg/mL

IL-4: 15.60± 3.96 pg/mL

IL-10: 68.80±11.23 pg/mL) (all P<0.01). The expression level of Scurfin protein on CD4+ CD25+ T cells of the imDC group (1.34±0.29) was significantly higher than that in the control (0.72±0.13)

CsA (0.37±0.11)

and mDC groups (0.78±0.17) (all P<0.05). Conclusion Donor-antigen-unloaded recipient-derived imDC is an effective treatment in inducing immune hyporesponsiveness through induction of T cell apoptosis

shift in Thl/Th2 balance

and prolifer- ation of regulatory T cell.