Matsuzaki G, Ogimoto M, Yoshikai Y, Seki R, Nomoto K
Department of Immunology, Kyushu University, Fukuoka, Japan.
Eur J Immunol. 1993 Dec;23(12):3345-9. doi: 10.1002/eji.1830231242.
The V gamma 5 chain of T cell receptor gamma delta is preferentially expressed by murine fetal thymocytes. The fetal V gamma 5 gene is known to be homogeneous and lacks N nucleotide addition. We previously reported that V gamma 5+ cells were detected among donor-derived thymocytes from irradiated C3H/He mice soon after reconstitution with AKR/J fetal liver (FL) cells, but that only a few V gamma 5+ were detected among donor-derived thymocytes from irradiated C3H/He mice reconstituted with adult bone marrow (ABM) cells. The results suggest that preferential use of V gamma 5 is determined at the level of T cell precursor generation. In the present report, we analyzed whether the junctional region of FL-derived V gamma 5 genes in the FL chimeras is of fetal type. Sequencing analysis showed that V gamma 5 genes from FL chimeras contained extensive N nucleotide addition and were diverse both in nucleotide sequences and deduced amino acid sequences. V gamma 5 genes from donor-derived thymocytes of ABM chimeras, which by polymerase chain reaction were revealed to be less frequent than those of FL chimeras, also showed extensive N addition. Furthermore, the terminal deoxynucleotidyl transferase (TdT) gene, which encodes an enzyme that adds N nucleotides into the junctional region, was expressed at high level in the donor-derived thymocytes of FL chimeras and normal 8-week-old AKR/J thymocytes but at low level in day 17 fetal AKR/J thymocytes. Our results suggest that the preferential rearrangement of the V gamma 5 gene is determined at the level of T cell precursor generation but the homogeneous V gamma 5 sequence of fetal type is generated only in the fetal thymic microenvironment where TdT gene expression is low or absent. The nomenclature of murine TcR gamma chains is according to Reilly et al. (Nature 1986. 321: 878). The relationship between the different nomenclature systems is summarized in Takagaki et al. (J. Immunol. 1989. 141: 2112).
T细胞受体γδ的Vγ5链在小鼠胎儿胸腺细胞中优先表达。已知胎儿Vγ5基因是同质的，且缺乏N核苷酸添加。我们之前报道，在用AKR/J胎儿肝脏（FL）细胞重建后不久，在受辐照的C3H/He小鼠的供体来源胸腺细胞中检测到Vγ5+细胞，但在用成年骨髓（ABM）细胞重建的受辐照C3H/He小鼠的供体来源胸腺细胞中仅检测到少数Vγ5+细胞。结果表明，Vγ5的优先使用是在T细胞前体产生水平上决定的。在本报告中，我们分析了FL嵌合体中FL来源的Vγ5基因的连接区是否为胎儿型。测序分析表明，来自FL嵌合体的Vγ5基因含有广泛的N核苷酸添加，并且在核苷酸序列和推导的氨基酸序列上都具有多样性。通过聚合酶链反应显示，ABM嵌合体供体来源胸腺细胞中的Vγ5基因比FL嵌合体中的频率更低，也显示出广泛的N添加。此外，编码将N核苷酸添加到连接区的酶的末端脱氧核苷酸转移酶（TdT）基因，在FL嵌合体的供体来源胸腺细胞和正常8周龄AKR/J胸腺细胞中高表达，但在第17天的胎儿AKR/J胸腺细胞中低表达。我们的结果表明，Vγ5基因的优先重排是在T细胞前体产生水平上决定的，但仅在TdT基因表达低或不存在的胎儿胸腺微环境中产生胎儿型的同质Vγ5序列。小鼠TcRγ链的命名法依据Reilly等人（《自然》1986年。321: 878）。不同命名系统之间的关系总结于Takagaki等人（《免疫学杂志》1989年。141: 2112）。
