细菌有一种对病毒的防御机制：一种叫做限制性内切酶的化学物质可以切断外源dna。

Bacteria have defences against viruses in the form of chemicals called restriction enzymes, which chop up foreign DNA.

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要在一种宿主表达系统中成功表达外源蛋白并获得较高产量，必须要较为全面地了解影响其表达的诸多因素。

Numerous factors that influence heterologous protein production in a certain host system must be observed to gain successful gene expression and even with high yields.

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NKT细胞是一种具有混合功能的细胞：它们既能如自然杀伤细胞般杀死入侵微生物，又能如t细胞般与抗原(能激发免疫反应的外源物质)结合。

NKT cells are hybrids: they kill invading microbes, like natural killer immune cells, but they also bind to antigens - foreign substances that trigger an immune response - like T-cells do.

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