IMMUNITY IN TRANSGENIC MICE

该研究项目的目标是进一步表征 抗体基因同种型转换的机制和调控。 三 已经假定相当不同的机制在同种型中是重要的， 开关：1）DNA开关重组; 2）选择性RNA加工， 长转录物;和3）RNA反式剪接。 有力的证据支持 染色体内DNA重组/缺失作为重要机制 参与抗体基因类别转换。 然而，我们发现， 鼠抗体μ重链转基因可经历同种型转换 并产生大量的IgG，以响应免疫接种。 合适的抗原。 令人惊讶的是，这种转基因同种型转换 反映了转基因之间的染色体间DNA重组事件 和内源性重链基因座，其导致染色体 易位，似乎是由正常的类转换介导的 重组机制 其他分析同种型转换的实验室 已经报道了转基因 转换显然可以通过RNA反式剪接机制发生。 我们 将进一步表征淋巴瘤杂交瘤中的转基因转换， 和来自我们的转基因小鼠的B细胞来探索 负责转基因转换的染色体间机制。 我们将 还研究了抗体重链的染色体间同种型转换， 非转基因小鼠中的链基因。 这些研究的一个组成部分将 包括研究染色体内和 染色体间转换 此外，我们将使用删除 诱变，以表征DNA序列元件的重要性， 转基因小鼠和突变小鼠中同种型转换过程 通过胚胎干（ES）中的同源重组诱变获得 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.