The AIP1 fraction, a small water-soluble fraction purified from Artemisia iwayomogi, was shown to increase antibody production and suppress transplanted tumor cell growth in mice. In order to understand its immunomodulating activity, we have examined the effect of the AIP1 on mouse thymocytes in vitro. Treatment of mouse thymocytes in culture with the fraction resulted in the suppression of the cell death and the extension of the cell survival. A mouse gene array provided a profile of gene expression change showing the pattern of up-and downregulated genes by the AIP1 treatment, suggesting that the Fas/FasL-dependent apoptosis pathway might be modulated by the fraction.

Apoptotic death of mouse thymocytes in vitro, as induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), involves the up-regulation of Fas gene expression, while a carbohydrate fraction, AIP1, from Artemisia iwayomogi suppresses the death of thymocytes in culture along with the down-regulation of Fas gene expression. We have now investigated whether the AIP1 fraction modulates TCDD-induced thymocyte death. When treated with TCDD and AIP1 fraction together, the thymocytes do not show apoptosis induced by the TCDD treatment. The AIP1 supplementation to the TCDD treatment also down-regulates the TCDD-induced Fas gene up-regulation. These findings indicate that the AIP1 fraction suppresses TCDD-induced thymocyte apoptosis through the modulation of Fas gene expression.