Dietary indole-3-carbinol alters immune functions in rats.

To further elucidate the physiological mechanisms that may contribute to the dichotomy of effect of indole-3-carbinol (I3C) on cancer development, we examined immune functions representative of the three major branches of the immune system in rats fed either a high (150 mg/kg) or low (50 mg/kg) dose of I3C. Animals fed the high dose of I3C daily for 7 wk had significantly reduced natural killer cell activity. In contrast, T-cell-mediated delayed-type hypersensitivity was significantly elevated. Antibody production in response to the antigen keyhole limpet hemocyanin was not significantly altered compared to controls. These results indicate that exposure to I3C may have differential effects on major immune responses. The significance of these immune function alterations in tumor development will require additional investigation of the effects of dietary I3C on immune functions in appropriate tumor models.