The cells that are activated in the adaptive immune response undergo clonal expansion which means that they massively proliferate.

在适应性免疫中被激活过的细胞会进扩增，意味着它们会大量增殖。

Once the pathogen is destroyed, most of the clonally expanded cells die off, that's called clonal deletion.

一旦病原体被摧毁了，大部分扩增的细胞会死亡，这被清除。

Either way, if the antigen is the right " fit" for the T cell, it will begin to differentiate and undergo clonal expansion.

无论哪种方式，如果抗原“适合”T细胞，那T细胞将开始分化并进扩增。

This is called clonal heterogeneity, and it makes treatment difficult because a drug that works on one subclone may have no effect on another.

这异质性，它使治疗变得困难，因对一个亚起作用的药物可能对另一个亚无效。

But, thanks to genetic testing, we've learned that this stand of aspen covering 106 acres of land is actually a single clonal organism that grew from a lone seed long ago.

不过，正是由于基因检测，我们发现这片覆盖 106 英亩的山杨实际上是由很长时间前的一粒种子无性繁殖出来的。