Immunological adjuvant effect of Glycyrrhiza uralensis saponins on the immune responses to ovalbumin in mice

In this study, the haemolytic activities of Glycyrrhiza uralensis saponins (GLS) and its adjuvant potentials on the cellular and humoral immune responses of ICR mice against ovalbumin (OVA) were evaluated. We determined the haemolytic activity of GLS using 0.5% rabbit red blood cell. Haemolytic percents of GLS-treated red blood cell were 11.20 and 5.54% at the concentrations of 500 and 250 μg/ml, respectively. ICR mice were immunized subcutaneously with OVA 100 μg alone or with OVA 100 μg dissolved in saline containing Alum (200 μg), QuilA (10 and 20 μg), or GLS (50, 100, or 200 μg) on Days 1 and 15. Two weeks later (Day 28), concanavalin A (Con A)-, lipopolysaccharide (LPS)-, and OVA-stimulated splenocyte proliferation and OVA-specific serum antibodies were measured. GLS significantly enhanced the Con A-, LPS-, and OVA-induced splenocyte proliferation in the OVA-immunized mice at a dose of 100 μg (P < 0.025). OVA-specific IgG, IgG1, and IgG2b antibody titers in serum were also significantly enhanced by GLS compared with OVA control group (P < 0.025). Moreover, no significant differences (P > 0.05) were observed between enhancing effect of GLS and QuilA on the OVA-specific IgG, IgG1, and IgG2b antibody responses to OVA in mice. The results suggest that GLS showed a slight haemolytic effect and enhanced significantly a specific antibody and cellular response against OVA in mice, and deserved further researches to be developed as immunological adjuvant.