Ginsenoside Rg1 enhances CD4(+) T-cell activities and modulates Th1/Th2 differentiation.

Panax ginseng is commonly used as a tonic medicine in Asian countries such as Korea, China, and Japan. It has been reported that ginsenoside Rg1 in P. ginseng increases the proportion of T helper (Th) cells among the total number of T cells and promotes IL-2 gene expression in murine splenocytes. This implies that ginsenoside Rg1 increases the immune activity of CD4(+) T cells, however, the exact mechanism remains unknown. The present study elucidated the direct effect of Rg1 on helper T-cell activities and on Th1/Th2 lineage development. The results demonstrated that ginsenoside Rg1 had no mitogenic effects on unstimulated CD4(+) T cells, but augmented CD4(+) T-cell proliferation upon activation with anti-CD3/anti-CD28 antibodies in a dose-dependent manner. Rg1 also enhanced the expression of cell surface protein CD69 on CD4(+) T cells. In Th0 condition, ginsenoside Rg1 increases the expression of IL-2 mRNA, and enhances the expression of IL-4 mRNA on CD4(+) T cells, suggesting that Rg1 prefers to induce Th2 lineage development. In addition, ginsenoside Rg1 increases IL-4 secretion in CD4(+) T cells under Th2 skewed condition, while decreasing IFN-gamma secretion of cells in Th1 polarizing condition. Thus, Rg1 enhances Th2 lineage development from the naïve CD4(+) T cell both by increasing Th2 specific cytokine secretion and by repressing Th1 specific cytokine production. Therefore, these results suggest that ginsenoside Rg1 is a desirable agent for enhancing CD4(+) T-cell activity, as well as the correction of Th1-dominant pathological disorders.