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，我们研究了在60ﾟC到90ﾟC的温度范围内，在10-300min的应用温度范围内，经或不经热处理的牛乳是否诱导了对牛β-乳球蛋白(β-LG)的口服耐受性。对(3-LG)反应较强的雌性C3H/HEN小鼠在接种β-LG前2-62天内，口服约3毫升/天/头的牛奶或热牛奶。用~3H-胸腺嘧啶核苷摄取法(T细胞增殖法)检测淋巴结细胞的体外抗原特异性增殖反应，并用酶联免疫吸附试验(ELISA)检测其血清与β-LG的结合。与对照组相比，饲喂生奶8天后，小鼠血清中抗β-LG抗体和T细胞应答水平均降低到1/10以下，即使在较长时间饲喂后，无反应状态也几乎保持不变。然而，喂养加热的牛奶并不能很好地诱导口服耐受性。这种对耐受性的抑制随着应用温度、时间和喂养时间的增加而逐渐增强。其次，我们研究了为什么用加热的牛奶喂养小鼠会导致耐受性差。分别给5组小鼠灌胃PBS(对照组)、β-LG、β-LG+乳糖、加热β-LG和加热β-LG+乳糖，比较各组小鼠的免疫耐受程度。只有加热的β-LG和加热的β-LG加乳糖组的口服耐受性受到显著抑制，提示β-LG和乳糖之间发生的氨甲酰(Maillard)反应可能降低天然蛋白抗原的口服耐受性。

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.