Athymic mice express a high level of functional gamma-chain but greatly reduced levels of alpha- and beta-chain T-cell receptor messages.
Athymic mice express a high level of functional gamma-chain but greatly reduced levels of alpha- and beta-chain T-cell receptor messages.
复制标题
无胸腺小鼠表达高水平的功能性γ链，但α链和β链T细胞受体信息的水平大大降低。
作者：
Y. Yoshikai;M. Reis;T. Mak
T淋巴细胞在胸腺中分化和成熟。正是在这里，对自身抗原具有反应性的胸腺细胞被消除，而对“改变的”自身主要组织相容性复合体（MHC）基因产物具有特异性的胸腺细胞被积极选择。这些选择可能是基于它们的T细胞抗原受体（TcR）进行的。已经克隆了α链和β链T细胞抗原受体的基因。第三个能够进行体细胞重排的T细胞特异性基因也已被鉴定;这第三个基因的作用尚不清楚。在T细胞个体发育过程中发现了γ、β、然后α的表达顺序。但是，尽管α链和β链信息通常是功能性的，但γ转录物在胸腺细胞或成熟T细胞中很少起作用。为了进一步确定这些基因表达的顺序，并继续寻找TcR γ基因产物的可能作用，我们研究了年轻无胸腺小鼠中“功能性”α，β和γ链转录物的表达。这些小鼠表达不可检测量（小于1/8 × 10（5）脾信息）的“全长”α和β链T细胞受体转录物，但“全长”γ链信息的表达水平增加。四个γ互补DNA的核苷酸序列分析表明，所有四个γ转录测序的功能。这些发现表明，γ基因产物可能是重要的胸腺前或胸腺外途径，并可能代表第二种类型的T细胞识别，可能在一个谱系中，α和β基因不使用。
T lymphocytes differentiate and mature in the thymus. It is here that thymocytes with reactivities to self antigens are eliminated and those with specificities to 'altered' self-major histocompatibility complex (MHC) gene products are positively selected. The selections are presumably carried out on the basis of their T-cell antigen receptors (TcR). The genes of the alpha- and beta-chain T-cell antigen receptors have been cloned. A third T-cell specific gene capable of undergoing somatic rearrangement has also been identified; the role of this third gene is not known. An order of expression of gamma, beta, then alpha is found during T-cell ontogeny. But although alpha- and beta-chain messages are often functional, gamma transcripts are rarely functional in thymocytes or mature T cells. To define the sequential order of expression of these genes further and to continue the search for a possible role for the TcR gamma gene products, we investigated the expression of 'functional' alpha-, beta- and gamma-chain transcripts in young athymic mice. These mice express an undetectable amount (less than one in 8 X 10(5) spleen messages) of 'full-length' alpha- and beta-chain T-cell receptor transcripts, but an increased level of expression of 'full-length' gamma chain messages. Nucleotide sequence analysis of four gamma complementary DNAs show that all four gamma transcripts sequenced are functional. These findings suggest that gamma gene products may be important in a prethymic or extrathymic pathway and may represent a second type of T-cell recognition, possibly in a lineage in which alpha and beta genes are not used.