Abstract: Objective To explore the effects of traditional Chinese formula Danchaiheji on the differentiation of regulatory dendritic cells (DCregs) and the underlying mechanism. Methods The rats’ serum with or without the treatment of formula Danchaiheji was prepared. The peripheral blood mononuclear cells were separated from the peripheral venous blood of healthy donors. CD14+ monocytes were isolated using CD14+ magnetic beads and cultured for 5–7 days to obtain immature dendritic cells (imDCs). Then the cells was divided into 4 groups, including the group of Danchaiheji containing rats’ serum after treatment of drug in the presence or absence of lipopolysaccharide (LPS) and the control group containing equal column rats’ serum in the presence or absence of LPS. Then the surface markers CD86, CD11b and HLA-DR of DCs were detected by flow cytometry and the levels of IL-10 were determined by enzyme-linked immunosorbent assays (ELISA). The proliferation of allogeneic T-cells was detected by flow cytometry and the expression level of indoleamine 2,3-dioxygenase (IDO) was determined using quantitative real-time PCR. Results DCs treated with the formula Danchaiheji exhibited high CD11b and low CD86 and HLA-DR expression levels as well as promoted the secretion of IL-10. In addition, the drug could inhibit the promotion of DCs on the proliferation of T cells, which is associated with the upregulation of IDO expression. Conclusion The traditional Chinese formula Danchaiheji could program DCs towards a regulatory DCs fate and the inhibitory effect on immune function was found.

Key words: dendritic cells, regulatory dendritic cells, immune tolerance, immunomodulation, IDO