Differentiation and maturation of human dendritic cells modulated by an exopolysaccharide from an anamorph of Cordyceps sinensis

Dendritic cells are central players in initiating and regulating immune responses. Effective induction of cell-mediated immune responses strongly depends on stimulating T cells by dendritic cells through antigen-presenting complex and co-stimulatory molecules. In this study, dendritic cells were differentiated from human peripheral blood mononuclear cells by using rhGM-CSF and rhIL-4. Then the effects of exopolysaccharide (EPS) from an anamorph of Cordyceps sinensis on human DCs were investigated. The results of flow cytometry showed that surface HLA-DR and co-stimulatory molecules of DCs were increased and DC's phagocytosis of FITC-dextran were significantly decreased after EPS treatment. EPS-treated DCs also displayed enhanced T cell stimulatory capacity in mixed lymphocyte reaction (MLR). ELISA and RT-PCR assay showed EPS increased IL-12 level of DCs. RT-PCR assay also showed EPS decreased VEGF mRNA level of DCs. Furthermore, Western blotting demonstrated that phosphorylated STAT3 were decreased after EPS treatment, suggesting that EPS stimulated the maturation of DCs probably by inhibiting STAT3 activation.