In vitro and in vivo immunosuppressive activity of Spica Prunellae ethanol extract on the immune responses in mice.

The immunosuppressive activity of the ethanol extract of Spica Prunellae (Prunella vulgaris fruiting spikes) (EESP) consisting of a mixture of triterpenoids, flavonoids, tannins and polysaccharide was studied on the immune responses in mice. The effects of EESP on mice splenocyte proliferation in vitro were measured. EESP significantly suppressed concanavalin A (Con A)- and lipopolysaccharide (LPS)-stimulated splenocyte proliferation in vitro in a concentration-dependent manner. Furthermore, the effects of EESP at three dose levels (a single dose of 0.25, 0.5, and 1.0 mg) on the humoral and cellular immune responses of mice subcutaneously immunized with ovalbumin (OVA) were examined. ICR mice were immunized subcutaneously with OVA on day 0 and 14. Starting on the day of immunization, the mice were administered subcutaneously with EESP at 0.25, 0.5, and 1.0 mg at intervals of 7 days for a total of five doses. On day 28, antigen-specific antibodies in serum, mitogen- and OVA-induced splenocyte proliferation were investigated. EESP significantly suppressed Con A-, LPS- and OVA-induced splenocyte proliferation in the immunized mice in a dose-dependent manner. Total IgG, IgG1 and IgG2b levels in the immunized mice were significantly reduced by EESP. Moreover, the suppressing effects on the antibody responses to OVA in the immunized mice were dose-dependently enhanced according to the increase of EESP. The results suggest that EESP could suppress the cellular and humoral response in mice.