Ex vivo stimulation of murine dendritic cells by an exopolysaccharide from one of the anamorph of Cordyceps sinensis.

Dendritic cells (DCs) play an important role in initiating antitumour immune response. Tumour progression usually induces defects in DC maturation and thus tumour-bearing hosts exhibit immunosuppression and tumour escape. The previous studies showed that an exopolysaccharide (EPS) from a fungus, one anamorph of Cordyceps sinensis, inhibited tumour growth via activating immune response in the hosts. In view of the crucial actions of DCs in antitumour immunity, the present study aims to explore the effects of EPS on murine DCs. Murine DCs were derived from the bone marrow of C57BL/6 mice, and the effects of EPS on phenotype molecules and ingestion function of DCs were assayed using flow cytometry. Cytokine expressions of DCs were assayed by reverse transcriptase-PCR. Additionally, the level of phosphorylated signal transducers and activators of transcription 3 (p-STAT3) of DCs was evaluated using Western blotting. The results showed that EPS promoted the levels of surface molecules MHC II, CD40, CD80 and CD86 of DCs and decreased their ingestion ability. The mRNA expressions of cytokines (IL-12p40 and TNF-α) and inducible nitric oxide synthase were up-regulated by EPS. We also found that EPS significantly down-regulated p-STAT3 level of DCs. The results suggested that the promotion of DC's maturation and activation by EPS is probably related to the inhibition of STAT3 phosphorylation.