We have found that alginic acid oligosaccharide (ALGO) enhanced Th1 by promoting IL-12 production, suggesting that ALGO can be applied as an anti-allergic food. In this study we examined both positive and negative functions of ALGO. First we investigated the anti-allergic activity of ALGO, as a positive function, when orally administered. IgE production was significantly inhibited in mice fed ALGO as compared to control mice. This result indicates that ALGO had antiallergic activity even when orally administered. On the other hand, we also found a negative function of ALGO. Oral co-administration of a protein antigen and ALGO inhibited the induction of oral tolerance to the protein.These data indicate the potential of ALGO as an antiallergic food material and the necessity of further examination to determine a safe method application.Key words: alginic acid oligosaccharide; anti-allergic food; IgE; IL-12; oral toleranceThe type I allergic reaction is mediated by the allergen-specific IgE antibody. The development of a method for inhibiting IgE production should therefore be a useful approach to preventing allergic disorders. In particular, IgE-inhibiting food materials can be expected to control allergic diseases through everyday meals. Several food materials have so far been studied and demonstrated to be anti-allergic. [1][2][3] We have found that alginic acid oligosaccharide (ALGO), which is a lyase lysate of alginic acid with an average degree of polymerization of 4.4, inhibited IgE production in a mouse model. 4) We also found that this function might be mediated by the IL-12-enhancing activity of ALGO, but in that study we examined only the IgE-inhibiting activity of ALGO when it was intraperitoneally administered. We considered that it would be necessary to test the activity of ALGO when it was orally administered to apply ALGO as an anti-allergic food material.In this present study we investigated the effect of orally administered ALGO on IgE production. Female BALB/c mice (6 weeks old; Clea Japan, Tokyo) were given 10 mg of ALGO dissolved in 200 ml of PBS five times by feeding needle. Each feed was given at an interval of 2-3 d. These mice were intraperitoneally immunized with 100 mg of bovine -lactoglobulin (-LG, genotype AA) mixed with 2 mg of an alum adjuvant after the second feed of ALGO. Two weeks after immunization, the mice were bled. The blood samples were centrifuged and the sera were collected. The -LGspecific IgE titer in the sera was measured by ELISA. Maxisorp immunoplates (Nunc, Roskilde, Denmark) were coated with a 0.01% -LG solution. After washing and blocking, the sample sera and standards were added to the plate. The bound antibody was detected with biotin-labeled rat anti-mouse IgE (LO-ME-2; Technopharm Biotechnology, Villejuif, France), before incubating with alkaline phosphatase-streptavidine. A substrate (p-nitrophenyl-phosphate) was then added, and the absorbance was determined at 405 nm. Student's t-test was used to analyze the statistical difference, a P value of less than 0.05 ...