Emodin inhibits the differentiation and maturation of dendritic cells and increases the production of regulatory T cells.

The aim of this study was to characterize the effects of emodin on dendritic cells (DCs) and CD4⁺CD25⁺ regulatory T cells (Tregs). Myeloid DCs were prepared from peripheral blood mononuclear cells of healthy human donors and treated with emodin at different concentrations. The phenotype and T cell stimulatory capacity of these DCs were analyzed. The expression ratios of CD80 and CD83 in DCs in the presence of emodin (100 µg/ml) were significantly decreased compared with that in DCs without emodin treatment (P<0.05). IL-12p70 production of DCs decreased significantly with emodin treatment (P<0.05). Furthermore, an approximately 2-fold decrease was observed in the ability of DCs pre-treated with emodin to induce T-lymphocyte proliferation. In addition, we found that emodin treatment increased the number of Tregs, which expressed lower levels of human leukocyte antigen (HLA-DR), glucocorticoid-induced tumor necrosis factor receptor (GITR), and cytotoxic T-lymphocyte associated antigen-4 (CTLA-4) as compared to cells without emodin treatment. Our results suggest that emodin inhibits the differentiation and maturation of DCs and induces Tregs, which may be helpful for the modulation of the immune rejection after liver transplantation.