Gene analysis of antibodies specific for allergen and antigenrelating to autoimmunity

为了阐明大类转换导致过敏性疾病的分子和细胞机制，我们在克隆水平上研究了与辅助性T细胞库相关的抗原特异性B细胞的分化过程。我们使用了含有β -乳球蛋白残基25-40 （F25-40）的肽片段，其中含有B细胞决定因素。与f25 -40特异性B细胞合作的T细胞库通过1)β - lg,2) f25 -40共轭载体蛋白或3)F21-40进行修饰。因此，我们通过比较引物B细胞库、类转换或引物抗原之间的亲和成熟，在克隆水平上证明了T细胞在B细胞分化中的辅助功能。因此，F21-40免疫不能诱导强烈的ⅱ类切换。与其他抗原不同，F21-40诱导的B细胞库中存在限制性V_H基因（J558）使用。这些结果表明，T细胞库与B细胞协同作用限制了B细胞库向ab分泌细胞的分化。为了确定这种限制的分子机制，我们分析了MHC II类分子与T细胞受体相互作用对B细胞活化的确切作用。结果表明，ii类介导的信号直接激活B细胞，促进lgG的产生。这些结果表明，ii类介导的信号在B细胞库的限制和类转换中起重要作用。

To elucidate the molecular and cellular mechanism of lgE-class switching leading to allergic diseases, we examined the differentiation process of antigen-specific B cells at a clonal level in related to the repertoire of helper T cells. We used a peptide fragment encompassing residues 25-40 (F25-40) of beta-lactoglobulin, which contained B cell determinant. T cell repertoire collaborating with F25-40-specific B cell were modified by priming with 1) beta-LG,2) F25-40-conjugated carrier protein or 3) F21-40. Thus, we demonstrate the helper functions of T cells in B cells differentiation at a clonal level by comparing primed B cell repertoire, class switching or affinity maturation among priming antigens. Consequently, the immunization with F21-40 could not induce strong lgG-class II switching. In addition, the restricted V_H gene usage (J558) was observed among B cell repertoire elicited by F21-40 distinct from other antigens. From these results, it has been suggested that T cell repertoire collaborating with B cells restrict B cell repertoire differentiating into Ab-secreting cells. To determine the molecular mechanism of the restriction, we analyzed the exact roles of the interaction between MHC class II molecules and T cell receptor on B cell activation. The results showed that the class II-mediated signals directly activate B cells and enhance lgG production. From these results, it has been suggested that the class II-mediated signals play an important role on the restriction of B cell repertoire and class switching.