Nutritional Status Enhancing Oral Tolerance against Dietary Antigens and its Physiological Mechanisms

利用卵清蛋白（OA）口服耐受动物模型，研究了膳食蛋白对OA口服耐受系统的影响。雌性BALB/c小鼠在腹腔注射OA蛋白前，以20%或5%蛋白质饲料喂饲OA（耐受组），除口服蒸馏水外，以上述相同方式制备致敏小鼠（致敏组）。OA致敏后，20%和5%蛋白饲料喂养的小鼠血清中总IgE升高，并诱导产生OA特异性抗体（IgE、IgG、IgG 1和IgG 2a）。致敏组中总IgE和OA特异性IgE在20%蛋白质饲料中高于5%蛋白质饲料。当口服该蛋白后用OA免疫小鼠时，饲喂5%蛋白质饮食的小鼠的总IgE和OA特异性抗体（包括IgE、IgG、IgG 1和IgG 2a）显著降低，而饲喂20%蛋白质饮食的小鼠几乎不受影响。在喂食20%和5%蛋白质饲料的小鼠中，致敏组和耐受组的脾细胞培养上清液中产生IL-4。在喂食5%蛋白质饮食的耐受组小鼠中细胞因子的产生量显著低于喂食20%蛋白质饮食的致敏和耐受组小鼠。在喂食20%和5%蛋白质饲料的致敏和耐受组小鼠中，脾细胞IFN-γ的恒定产生几乎消失。这些结果表明，低蛋白饮食更倾向于引入对饮食抗原的口服耐受，这可能归因于低蛋白饮食下调Th 2细胞因子。

Using animal model for oral tolerance against ovlbumin(OA), we investigated the effects of dietary proteins on the oral tolerance system. Female BALB/c mice were fed either 20% or 5% protein diet with oral administration of OA before intraperitoneal immunization of this protein(tolerated group), Sensitized mice were prepared by the same manner as above except for orally administration of distilled water(sensitized group). Sensitization of OA elevated total IgE and induced the production of OA specificantibodies(IgE,IgG,IgG1 and IgG2a) in serum in both mice fed 20% and 5% protein diet. Total IgE and OA specific IgE in the sensitized group were higher in mice fed 20% protein diet than in those fed 5% protein diet. When mice were immunized with OA after oral administration of this protein, total IgE and OA specific antibodies including IgE,IgG,IgG1 and IgG2a were significantly reduced in mice fed 5% protein diet but almost not effected in mice fed 20% protein diet. IL-4 was produced in spleen cell culture supernatants in the sensitized and tolerated groups in mice fed 20% and 5% protein diet. The amount of the production of the cytokine in the tolerated group of mice fed 5% protein diet was significantly lower than in the sensitized and tolerated group of mice fed 20% protein diet. The constant production of IFN-γ from spleen cells was almost disappeared in the sensitized and tolerated group in mice fed both 20% and 5% protein diet. These findings suggested that low protein diet prefer to introduce oral tolerance against dietary antigens, which might be attributed by down-regulation of Th2 cytokines in low protein diet.