foreign invaders that our immune system tries to defend us against.

免疫系统试图抵御的潜在外来侵略者
Because it's working to defend us

免疫系统的工作就是抵御
against many different kinds of potential assaults,

不同种类的潜在威胁
the immune system has a diverse repertoire of responses

免疫系统具备类型众多的免疫反应类型
that it uses in the face of these assaults.

以应对各种威胁
One kind of response is called the innate response

其中之一称为先天性免疫反应
and innate means that it's present from the beginning.

先天的意思是生来就有的
So, this is an immune response that doesn't have to be activated

所以这是一种不必激活的免疫反应
and we're used to thinking about immune responses that have to be activated.

我们曾认为免疫反应都需要激活
You get a vaccine for chicken pox,

当你拿到水痘疫苗
it gets injected,

并注射入体内后
and sometime later you're going to be protected against it.

一段时间之后你就可以免于感染