The immunomodulatory activities of the ethanol extract of Gynostemma pentaphyllum, termed hereafter as GPE,
were examined in immunosuppressed mice as well as in normal mice in the present study. Oral administration of GPE into mice
prevented dexamethasone (DEX)-induced immunosuppression as determined by the mitogen-induced proliferation of the splenocytes
and the the cytokine production (TNF-α, IL-1β) in the whole blood culture. In addition, oral administration of GPE
increased antitumor host defense in mice implanted with sarcoma-180 tumor cells. The immunoaugmenting activity of orally
administered GPE was also confirmed in mice immunized with ovalbumin (OVA). Mice that were orally administered with
GPE generated much more potent OVA-specific cytotoxic T lymphocyte (CTL) responses upon intravenous OVA injection
compared to the untreated controls. These results demonstrate that oral administration of the ethanol extract of Gynostemma
pentaphyllum could be useful to increase host defense in immunocompromised situations such as stress- or tumor-induced
immunosuppression.