Dendritic cell activation by polysaccharide isolated from Angelica dahurica

► ADP strongly activates dendritic cells to produce cytokines, decrease antigen uptake, and enhance allogenic T cell stimulation. ► ADP activates dendritic cells via binding to membrane receptor TLR4. ► ADP activates MAPKs and NF-κB signalings downstream from TLR4 in dendritic cells. Angelica dahurica is used in functional foods for the prevention and treatment of various diseases, such as inflammation and cancer. In the present study, we examined the effect of A. dahurica polysaccharide (ADP) on dendritic cell (DC) maturation. ADP increased the expressions of CD86 and MHC-II molecules, the production of IL-12, IL-1β, and TNF-α, and allogeneic T cell activation ability of DCs, and reduced DC endocytosis. As a mechanism of action, the knockdown of TLR4 with small interfering RNA decreased the ADP-induced production of nitric oxide and IL-12 by DCs, suggesting the membrane receptor candidate of ADP. After binding to TLR4, ADP increased the phosphorylation of ERK, JNK, and p38 MAPKs, and the nuclear translocation of NF-κB p50/p65. These results indicate that ADP activates DCs through TLR4 and downstream signalings.