Ginsenoside Rd elicits Th1 and Th2 immune responses to ovalbumin in mice

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Ginsenoside Rd (Rd), a saponin isolated from the roots of panax notoginseng, was evaluated for inducing Th1 or Th2 immune responses in mice against ovalbumin (OVA). ICR mice were immunized subcutaneously with OVA 100 μg alone or with OVA 100 μg dissolved in saline containing alum (200 μg), or Rd (10, 25 or 50 μg) on days 1 and 15. Two weeks later (day 28), concanavalin A (Con A)-, lipopolysaccharide (LPS)- and OVA-stimulated splenocyte proliferation was determined using MTT assay, and OVA-specific antibody titers and levels of cytokines in serum were measured by ELISA and microparticle-based flow cytometric immunoassay, as well as peripheral blood T-lymphocyte subsets analyzed using flow cytometer. Rd significantly enhanced the Con A-, LPS-, and OVA-induced splenocyte proliferation in the OVA-immunized mice. OVA-specific IgG, IgG1, and IgG2b antibody titers in serum were significantly enhanced by Rd compared with OVA control group. Meanwhile, Rd also significantly promoted the production of the Th1 and Th2 cytokines in OVA-immunized mice. Further, the effects of Rd on expression of cytokine mRNA in Con A-stimulated mice splenocytes were evaluated by RT-PCR analysis. Rd significantly enhanced the interleukin-2 (IL-2), interferon-γ (IFN-γ), IL-4, and IL-10 mRNA expression in mice splenocyte induced by Con A. These results suggested that Rd had immunological adjuvant activity, and elicited a Th1 and Th2 immune response by regulating production and gene expression of Th1 cytokines and Th2 cytokines.