TCR gene rearrangement in the peripheral lymphoid organs

我们建立了绿色荧光蛋白(GFP)基因敲除重组激活基因-2(RAG-2)敲除动物模型，用于检测外周淋巴器官中TCRαβ基因重排。RAG-2是T细胞和B细胞抗原受体基因重排所必需的。为了确定在胸腺以外的外周淋巴器官中发生TCR重排的T细胞亚群，我们建立了GFP基因敲除在RAG-2基因座上的小鼠(RAG2-GFP小鼠)。在RAG2-GFP小鼠的胸腺和骨髓中，正如预期的那样，在发育的T细胞和B细胞的适当阶段检测到GFP的表达。有趣的是，Peyer‘s Patch中的一小部分Thyl.2^+细胞被发现为GFP阳性。绿色荧光蛋白阳性细胞高表达表面TcRβ和CD3，提示成熟T细胞有TcRαβ重排。然而，连接介导的聚合酶链式反应分析发现，Jα和Dβ基因座的信号末端断裂显著水平。此外，从TcRα和TcRβ基因座产生的环状DNA的水平与总胸腺细胞的水平相当。这些结果表明，部分佩耶氏斑T细胞存在TcR、α和β基因的二级重排事件。

We have established GFP (green fluorescence protein) gene knock-in Recombination activating gene-2 (RAG-2) -knockout animals to detect TCRαβgene rearrangement in the peripheral lymphoid organs. RAG-2 is essential for gene rearrangement of both antigen receptors of T and B cells. To identify T cell subpopulations undergoing TCR rearrangement in the peripheral lymphoid organs other than the thymus, we established mice in which a GFP gene is knocked in the RAG-2 gene locus (RAG2-GFP mice). In the thymus and bone marrow of RAG2-GFP mice, as expected, GFP expression was detected in appropriate stages of developing T cells and B cells. Interestingly, a fraction of Thyl.2^+ cells in the Peyer's Patch are found to be GFP-positive. The GFP-positive cells express high levels of surface TCRβ and CD3 on the surface, suggesting mature T cells with rearranged TCRαβ. However, significant levels of signal-end breaks of Jα and Dβ locus were detected by ligation-mediated PCR analysis. Moreover, circular DNAs generated from TCRα and TCRβ gene locus were detected at levels comparable to those of total thymocytes. These results suggest that there exist secondary rearrangement events of TCR α and β gene in a fraction of the Peyer's Patch T cells.