Fumonisin B(1) (FB(1)) is a mycotoxin produced by Fusarium verticillioides and F. proliferatum, common contaminants of maize. FB(1) causes toxicological effects in laboratory and domestic animals including pigs. The gastrointestinal tract represents a barrier encountered by exogenous food compounds. The purpose of our study was to determine FB(1) effects on intestinal immune response. Nine recently weaned piglets orally received 0.5 mg of purified toxin/kg of body weight/day for 7 days, while eight other animals were kept as controls. After necropsy, ileal samples were analyzed for five pro-inflammatory cytokines mRNA expression by RT-PCR. No difference was observed for IL-1beta, IL-6, IL-12 and TNF-beta mRNA levels between control and FB(1)-treated animals. In contrast, FB(1) treatment induced a significant down-regulation of the expression of IL-8 mRNA in the pig ilea. The effect of FB(1) on the IL-8 expression was also examined in the porcine intestinal epithelial cell line IPEC-1. FB(1) decreases the expression of IL-8, both at the mRNA and protein levels, in a dose-dependant manner. Taken together, our data demonstrate that FB(1) alters the intestinal immune response by decreasing the level of IL-8. This may contribute to the increased intestinal colonization by pathogenic Escherichia coli that was observed in FB(1)-treated pigs and may have implications for humans/animals consuming FB(1)-contaminated food/feed.