Study on the immune adjuvant effect of saponins from Panax ginseng and Panax ginseng
Saponins are steroid or triterpenoid glycosides widely present in some plants, and with further research, they have also been used as a plant derived adjuvant in vaccines. Research has shown that oral administration of saponins has a certain adjuvant effect. For example, oral administration of resveratrol can enhance the immune effect of ovalbumin (OVA), while oral administration of ginsenosides from ginseng stems and leaves can significantly increase the specific IgG and subclass titers in the serum of mice injected with foot-and-mouth disease vaccine, promote spleen lymphocyte proliferation, upregulate mRNA expression of related genes, and enhance response effects. Radix Pseudostellaria fibroblast roots saponins (RPFRS) are active ingredients extracted from the ginseng roots of Pseudostellaria heterophylla, which have the effects of enhancing the body’s immunity, antioxidation, and stress resistance. Nowadays, the main root of Panax ginseng is used as medicine, while the root silk is discarded, causing great waste. Research has found that the average content of total saponins in the root silk of Panax ginseng is 1.14 times that of the root tuber. The preliminary experiments of the research group have shown that the extract of Panax ginseng ginseng and ginseng beard, which contains saponins as one of its components, can enhance the immune response of immune damaged mice and has a significant regulatory effect on immunity. It is speculated that it may have the potential to enhance the immune response of the body to antigens. However, there are few reports on the effect of saponins from Panax ginseng and Panax ginseng on assisting antigen immunity in the body. Studies often use OVA as a model antigen to verify the efficacy of adjuvants. Model antigens induced by OVA produce higher IgG responses, and the proliferation ability of mouse spleen cells, as well as the mRNA expression of cytokines IL-4, IL10, IL-12, IFN – γ, transcription factors GATA-3, and T-bet, are also improved. Therefore, in this experiment, the immune adjuvant effect of oral administration of RPFRS on OVA model antigen immunized mice was studied, and its related immunological indicators were detected to explore the immune adjuvant effect and possible mechanism of RPFRS on OVA model antigen. This provides a theoretical reference for further searching for efficient, non-toxic, and safe traditional Chinese medicine immune adjuvants.

 

T. B cells can recognize antigens, activate the body’s immune system, and activate cell proliferation. The ability to induce effective T and B lymphocyte immune responses can be demonstrated by stimulating lymphocyte proliferation reactions. Ginsenosides from ginseng stems and leaves can enhance the efficacy of foot-and-mouth disease vaccine and stimulate lymphocyte proliferation under ConA and LPS stimulation, respectively; Panax notoginseng saponins can significantly enhance the proliferation of spleen cells induced by ConA, LPS, and OVA in mice immunized with OVA. The results of this experiment showed that group Z can synergistically promote the proliferation of mouse spleen lymphocytes with ConA, while groups Z and G can more significantly synergistically promote the proliferation of mouse spleen cells with LPS and OVA, indicating that RPFRS can enhance humoral and cellular immunity by promoting spleen cell proliferation, and has an effect on improving T and B cell viability in immunized OVA mice.

NK cells have a natural killing function, and the activation of the body’s innate immunity can promote the secretion of NK cells, playing a crucial role in autoimmune diseases. Li et al. found that ginsenoside Rb1 can reduce the NK cell killing effect inhibited by dasatinib. The results of this experiment indicate that the RPFRS group can improve NK cell activity to a certain extent, and low-dose RPFRS is more effective, resulting in a higher killing rate of YAC-1. This proves that RPFRS can enhance the cellular immune process of immune OVA mice and enhance their non-specific immune function.

Th cells include Th1 cells (producing IFN – γ, IL-2, etc.) and Th2 cells (producing IL-4, IL-6, IL-10, etc.). Th1 cells can activate pro-inflammatory responses, promote macrophage activation, and CTL cell proliferation; Th2 promotes the activation, proliferation, and antibody production of B cells, and the balance between Th1 and Th2 regulates the immune response of the body. The results of this experiment showed that the levels of IL-2, IL-4, IL-10, and IFN – γ cytokines increased in the RPFRS group, indicating that RPFRS can promote Th2 type and Th1 type immunity, increase cytokine secretion, and thus promote the body’s immunity. From this, it can be seen that oral administration of RPFRS has a promoting effect on both types of immunity, which can provide broader development space for its clinical application.

The production of antibody subclasses in the body is influenced by different cytokines. Th1 cytokines promote the production of IgG2a by B cells, while Th2 cytokines promote the production of IgG1 by the body. Sun et al. found that the combination of protopanaxadiol and triol saponins with OVA can enhance the OVA specific antibody IgG of immunized mice. The AJS75 component of total saponins from Acacia bark was also found to significantly enhance the immune potency of OVA and activate Th1/Th2 response in mice. The results of this experiment indicate that each dose of RPFRS group can increase the content of OVA specific IgG antibodies and their subclasses more than the OVA group, indicating that RPFRS can promote Th1 and Th2 type immunity, stimulate the secretion of specific antibodies in the body, which is consistent with the results in the above literature.

T-bet and GATA-3 are closely related to the differentiation of Th1/Th2, and they can affect the dynamic balance between Th1/Th2 by regulating cytokine secretion and mRNA expression. Su’s research shows that ginsenosides Rg1 and Re can enhance the immune response of mice induced by OVA by increasing the mRNA expression of related cytokines such as IFN – γ. The experiment conducted by Wang et al. on mice showed that the combination of total saponins from ginseng stems and leaves and selenium can act as an adjuvant to the immune response of attenuated rabies vaccine by upregulating the expression of T-bet/GATA-3 mRNA. The results of this experiment indicate that medium dose RPFRS can significantly increase the expression of IL-4mRNA, high dose RPFRS can significantly promote the expression of IL-10mRNA, and all RPFRS groups can to some extent increase the expression of T-bet, GATA-3, and T-bet/GATA-3 ratio, indicating that RPFRS can promote the production of Th1/Th2 response by promoting the expression of relevant cytokines and transcription factor mRNA, thereby enhancing the cellular immune function of the body and strengthening the body’s response to OVA.

The T lymphocyte subpopulation reflects the overall cellular immune status of the body. The number of CD3+, CD4+, CD8+T cells and the balance of CD4+/CD8+ratio can indicate the immune status of the body, among which CD4+and CD8+T cells are mainly mediated by cellular immunity. Qi et al. found that ginsenoside Rh2 and its main metabolites R-PHQ and S-PHQ can enhance the immune response of cyclophosphamide induced immunocompromised mice by preventing immune organ atrophy, promoting spleen cell proliferation, and restoring CD4+/CD8+ratio. The results of this experiment indicate that compared to the OVA group, each group of RPFRS can significantly increase the number of CD3+, CD8+T cells and the CD4+/CD8+ratio. The D and Z groups can significantly increase the number of CD4+T cells, indicating that RPFRS has the effect of balancing the body, enhancing T cell immunity, and increasing immune response.
The results determined by the above indicators show that RPFRS can enhance the humoral and cellular immune responses of OVA immunized mice, and can generate a more sustained response and improve mouse immune function than OVA immunized control mice. This proves that RPFRS has good potential as an immune adjuvant. In the experiment, different doses of Panax ginseng saponins showed advantages in certain indicators, so further screening is needed for the optimal concentration. At the same time, the specific effective components and mechanisms of action of Panax ginseng saponins have not been fully elucidated and need further research.