IMMUNITY IN TRANSGENIC MICE

这项研究项目的目标是进一步描述 抗体基因同型转换的机制及调控。三 完全不同的机制被认为在同种异型中很重要 开关：1)DNA开关重组；2)选择性RNA加工 长转录本；以及3)RNA反式剪接。强有力的证据支持 染色体内DNA重组/缺失是一种重要机制 参与抗体基因类型的转换。然而，我们发现一个 鼠抗体Mu重链转基因可进行同型转换 并产生大量的免疫球蛋白以回应免疫 合适的抗原。令人惊讶的是，这种转基因同型转换 反映了转基因之间的染色体间DNA重组事件 以及导致染色体的内源性重链基因座 易位，似乎是由正常的类开关调节的 重组机制。其他实验室分析同型转换 有报道称，一种人类抗体重链转基因 显然，转换可以通过RNA反式剪接机制发生。我们 将进一步描述淋巴瘤杂交瘤中的转基因转换， 从我们的转基因小鼠中提取的B细胞来探索 负责转基因转换的染色体间机制。我们会 也研究了抗体Heavy的染色体间同型转换 非转基因小鼠的链基因。这些研究的一个组成部分将是 包括调查染色体内和染色体内的相对频率 染色体间的转换。此外，我们还将使用删除 用诱变技术来鉴定DNA序列元件，这些元件对 转基因小鼠和突变小鼠的同型转换过程 胚胎干细胞中同源重组突变衍生的研究 细胞。

The goal of this research project is to further characterize the mechanisms and regulation of antibody gene isotype switching. Three quite distinct mechanisms have been postulated to be important in isotype switching: 1) DNA switch recombination; 2) alternative RNA processing of long transcripts; and 3) RNA trans-splicing. Strong evidence supports intrachromosomal DNA recombination/deletion as an important mechanism involved in antibody gene class switching. However, we have found that a murine antibody mu heavy chain transgene can undergo isotype switching and produce large amounts of IgG in response to immunization with the appropriate antigen. Surprisingly, this transgene isotype switching reflects interchromosomal DNA recombination events between the transgene and the endogenous heavy chain gene locus which result in chromosomal translocations and which appear to be mediated by the normal class switch recombination mechanisms. Other laboratories analyzing isotype switching of a human antibody heavy chain transgene have reported that transgene switching can apparently occur by an RNA trans-splicing mechanism. We will further characterize transgene switching in lymphomas hybridomas, and B-cells derived from our transgenic mice to explore the interchromosomal mechanisms responsible for transgene switching. We will also investigate interchromosomal isotype switching of antibody heavy chain genes in non-transgenic mice. A component of these studies will involve investigating the relative frequencies of intrachromosomal and interchromosomal switching. In addition, we will use deletional mutagenesis to characterize DNA sequence elements important for the isotype switching process both in transgenic mice and in mutant mice derived by homologous recombination mutagenesis in embryonic stem (ES) cells.