Inhibitory Effects of Amino-carbonyl Reactions Occurred between bovine beta-lactoglobulin and Lactose on the Oral Tolerance-inducing Activity of the Native Protein Antigen.

在本研究中，我们研究了牛β -乳球蛋白（β - lg）是牛奶中最有效的过敏原之一，在加热或不加热的情况下，在60 - 90ºC的温度范围内喂养10-300分钟，是否会诱导奶牛对β -乳球蛋白（β - lg）的口服耐受。对（3 -Lg）反应较高的雌性C3H/HeN小鼠组在接种β -Lg前2-62天口服约3毫升/天/头的乳汁或加热乳汁。然后通过测量^ 3h -胸腺嘧啶摄取（T细胞增殖试验）检测淋巴结细胞的体外抗原特异性增殖反应，并通过酶联免疫吸附试验（ELISA）研究其血清与β -Lg的结合。与对照组相比，原乳喂养8天通常会将抗体和T细胞对β - lg的反应水平降低到1/10以下，即使喂养时间更长，无反应状态也几乎保持不变。然而，通过喂养加热后的牛奶不能很好地诱导口服耐受性。这种对耐受性的抑制作用随着施加温度、时间和饲喂时间的增加而逐渐增强。接下来，我们研究了加热牛奶喂养小鼠导致耐受性差的原因。五组小鼠分别口服PBS（对照）、β - lg、β - lg加乳糖、加热β - lg和加热β - lg加乳糖，比较各组小鼠的免疫耐受程度。只有加热后的β -Lg加乳糖组对β -Lg和加热后的β -Lg加乳糖均有明显的口服耐受性抑制，这表明β -Lg和乳糖之间发生的氨基羰基（美拉德）反应可能降低了天然蛋白抗原的口服耐受性诱导活性。

In the present study, we examined whether oral tolerance directed against bovine beta- lactoglobulin (beta -Lg), one of the most potent allergens in cow's milk, was induced by feeding of cow's milk with or without heat treatments at the applied temperature ranging from 60ﾟC to 90 ﾟC for a period of 10-300 min. Groups of female C3H/HeN mice, a higher responder to (3 -Lg, were orally given with about 3 mI/day/head of the milk or heated milk during 2-62 days prior to the immunization with beta-Lg. The lymph node cells were then tested for their in vitro antigen-specific proliferative response by measuring ^3H-thymidine uptake (T cell proliferation assay) and their sera were also investigated for the binding to beta -Lg by an enzyme-linked immunosorbent assay (ELISA). The feeding of raw milk for 8 days was usually found to lower the both levels of antibody and T cell responses against beta-Lg to less than 1/10 as compared with the control mice, and the unresponsiveness state was held almost constant even after the longer feeding of the milk. The oral tolerance, however, could not be well induced by feeding of the heated milk. Such inhibition of the tolerance was gradually enhanced with increasing the applied temperature, time and the feeding period.Next, we studied why the poor tolerance was induced by feeding with the heated milk in mice. Five groups of mice were orally administrated with PBS (control), beta-Lg, beta-Lg plus lactose, heated beta-Lg and heated beta-Lg plus lactose, respectively, and compared the magnitude of immunological tolerance observed in each group of mice. The significant inhibition of oral tolerance specific for both beta-Lg and heated beta-Lg plus lactose was shown in only the group given with heated beta-Lg plus lactose, suggesting that amino-carbonyl (Maillard) reactions occurred between beta- Lg and lactose may lower the oral tolerance-inducing activity of the native protein antigen.