Ginsenoside Rg1 Activates Dendritic Cells and Acts as a Vaccine Adjuvant Inducing Protective Cellular Responses Against Lymphomas

Ginsenoside, a natural triterpenoid saponin, exhibits immunomodulatory and anticancer activities. In the present study, we demonstrated that ginsenoside Rg1 induced secretion of cytokines, including interleukin (IL)-6, tumor necrosis factor-alpha (TNF-alpha), and IL-1 beta, and chemokines such as IL-8 and IP-10 in a dose-dependent manner by human peripheral blood mononuclear cell (PBMC)-derived dendritic cells. Rg1 stimulated the expression of the surface molecules CD83, CD80, and human leukocyte antigen - antigen D related (HLA-DR) and decreased the expression of CD14. In in vivo experiments, C57BL/6 mice were divided into four groups, immunized with ovalbumin (OVA), OVA plus Rg1, Rg1, and phosphate-buffered saline (PBS), respectively. Splenocytes from C57BL/6 mice immunized with OVA plus Rg1 produced more antigen-specific splenocyte proliferation activity. The level of IFN-gamma and IL-4 in the splenocytes was also upregulated when in vitro stimulated with OVA(257-264) or OVA. After in vivo injection of tumor-forming E. G7-OVA cells, the survival rate of mice immunized intraperitoneally in OVA plus Rg1 immunized mice was higher than that in OVA immunized mice or PBS immunized mice. Thus, Rg1 induced a potent vaccine adjuvant effect and elicited antitumor immunity that polarized a Th1 type immune response. Rg1 could have potential as a prophylactic vaccine adjuvant to control lymphomas.