Rehmannia glutinosa polysaccharide functions as a mucosal adjuvant to induce dendritic cell activation in mediastinal lymph node

In our previous study, we showed that Rehmannia glutinosa polysaccharide (RGP) treatment induced activation of dendritic cells (DCs) in human and mouse subjects. In this study, we evaluated the effect of RGP as a mucosal adjuvant for inducting activation of DCs in the mediastinal lymph node (mLN) in the mouse. The C57BL/6 mice were intranasally (i.n.) treated with RGP and activation of DC in the mLN was analyzed. The treatment with RGP induced a substantial increase in the number of DCs in the mLN due to the up-regulation of C-C motif chemokine receptor 7 (CCR7) in the DCs. Moreover, the expression of co-stimulatory molecules in the mLN DCs and the concentration of pro-inflammatory cytokines in the lung were up-regulated by RGP treatment. Also, RGP treatment induced interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α) production in the mLN T cells. The combination treatment of RGP and ovalbumin (OVA) induced OVA-specific TCR transgenic I (OT-I) and OT-II cell proliferation in the mLN. Finally, the combination treatment of RGP and tyrosinase-related protein 2 (TRP2) peptide, a melanoma self-antigen, protected mice from melanoma challenge. Thus, these data demonstrated that RGP can be used as a mucosal adjuvant for inducing activation of immune responses in the lung.