Inhibition of T-cell proliferation by induction of IDO in spleen-derived dendritic cells of rats

Objective To investigate the expression chenges of indoleamine 2,3-dioxygenase (IDO) mRNA and protein in dendritic cells (DCs) derived from rat spleen in vitro as well as the effect of IDO on proliferation of allogeneic T lymphocytes in terms of different concentrations of interferon (IFN)-γ.Methods We first extracted DCs from the spleen of rats,then measured the expression of DC-specific molecules and surface molecules CD80 and CD86 in rats by flow cytometry.DCs were induced by IFN-γ at differenct concentrations (0,100,300,500 U/ml).Real-time polymerase chain reactio (PCR) and Western blotting were used to detect the relative expression levels of IDO mRNA and protein in DCs.Allogeneic mixed lymphocyte reaction (MLR) was applied to test the effect of DCs induced with different concentrations of IFN-γ on allogeneic T lymphocyte proliferation.Results The results showed that the spleenderived DCs from rats cultured for 10 days had a typical dendritic morphology,whose expression rate of OX62 was above 80％ and positive expression rate of CD80 and CD86 was more than 75％ and 90％ respectively.The expression levels of IDO mRNA ( 1.010 ±0.094,1.340 ±0.114,1.700 ±0.087,2.080±0.150) and protein (0.861 ±0.612,1.155 ±0.059,1.308 ±0.068,1.755 ±0.118) were increased gradually with the increase of concentrations of IFN-γ,which showed significant difference between any two groups.As compared with the control group,the groups induced by the IFN-γ had a decrease in T lymphocyte proliferation of DCs (P ＜ 0.05 ).Besides,with the increased concentration of IFN-γ,the rate of T lymphocyte proliferation was decreased gradually and there was significant difference between ant two groups (P ＜0.05).Conclusion The IFN-γ can induce the increased expression of IDO in spleen-derived DCs from rats,and the decreased stimulation capacity of spleen DCs to the antigen-specific T cell response. Key words: Dendritic cell; Indoleamine 2,3-dioxygenase; γ-interferon; T lymphocyte