Rehmannia glutinosa polysaccharide promoted activation of human dendritic cells

In our previous study, we showed that Rehmannia glutinosa polysaccharide (RGP) treatment induced maturation of dendritic cells (DCs) and that it had an anticancer effect in mice. The effect of RGP has not been studied in human DCs, including monocyte-derived DCs (MDDCs) and peripheral blood DCs (PBDCs). In this study, we examined DC activation by RGP in human cells. The dendritic morphology of RGP-treated MDDCs was substantially altered as compared with that of phosphate-buffered saline (PBS)-treated control cells. Moreover, RGP treatment markedly decreased phagocytic activity and increased expression levels of co-stimulatory molecules in MDDCs. In addition, RGP treatment elevated the production of proinflammatory cytokines. Furthermore, RGP-induced activation of MDDCs was dependent on the phosphorylation of extracellular signal-regulated kinase (ERK), p38, and c-Jun N-terminal kinase (JNK). RGP-treated MDDCs promoted upregulation of T-cell activation, including proliferation and interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α) production. Analysis of the effect of RGP in PBDC subsets revealed that it induced upregulation of co-stimulatory molecule expression and proinflammatory cytokine production. These data suggest that RGP may function as an immune stimulatory molecule in humans.