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  三、T细胞库的多样性

  推测T细胞库(T cell repertoire)中多样性在1010以上,其多样性的原因与Ig相似,主要有以下几方面。

  1.胚系中有众多的V、D和J基因片段 尽管TCRα和β基因中V基因片段数比Ig基因少,但J基因片段明显比Ig基因为多,如小鼠中约50~100个Jα和至少12个Jβ基因片段,而IgH和κ链基因座中J基因片段各只有4个。

  2.连接处连接的多样性 与IgVDJ连接的多样性相似。

  3.N区的插入 N区插入在Ig基因重排中只发生在重链基因,而TCRα和β链基因均可发生N区的插入。此外,在TCRα和β链基因中都发现一种称之为“易变性”(flexibility)的现象,如有一个以上Vα基因3′端可以连接到Jα片段。

  4.TCRα与β链的随机配对 人TCRαβ库多样性可推算为:α链(Vα(100)×Jα(100))×β链(Vβ(100)×Dβ(2)×Jβ(14))=2.8×107,这种多样性尚未包括N区插入所扩展的多样性。

(金伯泉)

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