T-cell proliferation is inhibited by the induction of indoleamine 2,3-dioxygenase in spleen-derived dendritic cells in rat.

BACKGROUND: Increasing evidence suggests that, by the production of indoleamine 2,3-dioxygenase (IDO), dendritic cells (DC) may reduce the activity of T lymphocytes and inhibit T lymphocyte proliferation-induced immune tolerance. One promising way is inspired by increasing IDO expression in DC cells for immune tolerance after transplantation. The aim of this work was to examine the effect of interferon-γ (IFN-γ) on the expression of IDO by DC. METHODS: Spleen-derived rat DCs were cultured and induced by cytokines, and the expression of OX62 and surface molecules CD80 and CD86 were measured with flow cytometry. After the DCs were induced by IFN-γ at different concentrations (0, 100, 300, 500 U/ml), the expression levels of IDO mRNA were measured with real-time PCR, and the expression levels of IDO protein in DCs were measured with Western blotting. The allogeneic mixed lymphocyte reaction (MLR) was used to test the effects of DCs incubated with different concentrations of IFN-γ on allogeneic T lymphocyte proliferation. RESULTS: Under the microscope, the DCs induced by IFN-γ showed a typical dendritic morphology. The expression rate of OX62 was above 80% and the positive expression rates of CD80 and CD86 were both about 80%. The expressions of IDO mRNA and IDO protein increased gradually with the increase of IFN-γ concentration, showing statistical significance in the differences between the groups (P < 0.05). Compared with the control DC, the DC incubated with IFN-γ had a notable decrease in allostimulatory activity (P < 0.05). With the increasing IFN-γ concentration, the T lymphocyte proliferation decreased, and the difference between the groups was also statistically significant (P < 0.05). CONCLUSIONS: The highly purified spleen derived rat DCs can be successfully acquired through the improved adhesion in-vitro method. IFN-γ can induce increased expression of IDO in spleen-derived rat DCs and reduce the spleen DCs' capacity to stimulate the proliferation of allogeneic T cells.