Immunoadjuvant activity in mice of polysaccharides isolated from the leaves of Panax ginseng C.A. Meyer.

Our previous study showed polysaccharide (GS-P) isolated from the leaves of Panax ginseng C.A. Meyer possessed anti-tumor metastatic activity in mouse model. In this study, we evaluated the immunoadjuvant effect of GS-P on the induction of humoral and cellular immune responses against ovalbumin (OVA) in mice. When mice were immunized subcutaneously with OVA admixed with or without GS-P, the OVA+GS-P group showed significantly higher antibody production than the group immunized with OVA alone. This suggests that GS-P has the ability to enhance the adaptive immune response. In addition, the OVA+GS-P+FIA (Freund's incomplete adjuvant) group induced higher levels of antigen-specific IgG1 and IgG2b antibodies than the OVA+FIA group. The culture supernatant obtained from the splenocytes of mice immunized with OVA+GS-P+FIA showed higher levels of OVA-specific Th1-type (IL-2, IFN-γ, GM-CSF) and Th2-type (IL-10) cytokines. Following in vitro analysis of T cell proliferation, the splenocytes of mice treated with OVA+GS-P+FIA showed significantly more proliferation than those treated with OVA+FIA. Further, the production of IgE antibody was dramatically reduced when OVA+GS-P+FIA was used to immunize mice rather than OVA+FIA or OVA+FCA (Freund's complete adjuvant). Collectively, these results suggest that GS-P may possess adjuvant activity that potentially enhances humoral as well as cellular immune responses.