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

采用口服卵蛋白耐受动物模型，研究了膳食蛋白对口服耐受系统的影响。给雌性BALB/c小鼠灌胃20%或5%的蛋白质饲料，同时灌胃给予OA(耐受组)，致敏小鼠除灌胃蒸馏水外，其余方法同上。在饲喂20%和5%蛋白质饲料的小鼠中，OA致敏均可提高血清总IgE水平，并诱导血清中OA特异性抗体(IgE、Ig G、Ig G1和Ig G2a)的产生。20%蛋白质饲料致敏组小鼠血清总IgE和OA特异性IgE均高于5%蛋白质饲料组。口服该蛋白后用OA免疫小鼠，能显著降低5%蛋白质饲料小鼠的总IgE和OA特异性抗体IgE、Ig G、Ig G1和Ig G2a，而对20%蛋白质饲料小鼠几乎没有影响。在饲喂20%和5%蛋白质饲料的致敏和耐受组小鼠脾细胞培养上清液中可产生IL-4。5%蛋白质饲料耐受组小鼠细胞因子的产生量明显低于20%蛋白质饲料致敏耐受组小鼠。用20%和5%蛋白质饲料喂养的致敏耐受组小鼠，脾细胞持续产生干扰素-γ的能力几乎消失。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，这可能是由于低蛋白饮食中Th2细胞因子的下调所致。

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.