Objective: To investigate the effect of tolerogenic dendritic cells (Tol-DC) generated by Rapamycin (Rapa) on the differentiation of Treg/Th17 cells and explore the possible mechanism of tolerance induction.
Methods: DC progenitors from mouse bone marrow were propagated with granulocyte-macrophage colony-stimulating factor (GM-CSF) plus interleukin (IL)-4 stimulation for 6 days in the presence or absence of Rapa (20 ng/ml). During DC culture, morphology of cell was observed under electron microscope. Cell surface expression of CD11c, CD40 and CD80 was analyzed by flow cytometry. The antigen-presenting function of DC was determined by one-way mixed leukocyte reactions. In vivo, the recipient BALB/c mice receiving transplantation of skin allograft from C57BL/6 mice were divided into control, Rapa, immature DC (imDC) and Tol-DC group. The survival time of the skin allograft was observed and Treg/Th17 cells were analyzed by flow cytometry in each group.
Results: The immunephenotypic analysis showed that in comparison with those in the control group and the LPS group the expression of the co-stimulatory molecules CD40 and CD80 were significantly lower in the Rapa-group and Rapa+LPS group. The ability to stimulate proliferation of T cells of the same genotype in the Rapa-group was significantly inhibited (P<0.01). In the in vivo experiment, the mice's survival time remarkably prolonged, the percentage of Treg cells was enhanced and Th17 cells was reduced in the mice's spleen in Tol-DC group.
Conclusions: Tol-DC generated by Rapamycin can significantly induce immune tolerance through up-regulate Tregs and down-regulate Th17 cells. The present study highlights the therapeutic potential of preventing allograft rejection using in vitro-generated Tol-DCs, which can be loaded with donor antigen, and potentially used to promote organ transplant tolerance.