处女地流行病指的是那些风险人群以前没有接触过袭击他们的疾病，因此在免疫上几乎毫无防御能力的疾病。

Virgin-soil epidemics are those in which the populations at risk have had no previous contact with the diseases that strike them and are therefore immunologically almost defenseless.

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与此相反的是，幼龄儿童没有与H1N1的既往接触史，故而免疫系统无法及时作出反应。

The very young children, in contrast, represent the responses of immune systems that have no past history with H1N1.

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平心而论，牛皮廯与自身免疫系统有关，即使你从不接触香烟，它也可能会出现。

To be fair, psoriasis is an autoimmune-related skin condition that can show up even if you never touch a cigarette.

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Memory cells are long lasting cells that remember this exposure and can respond very quickly on second exposure.

记忆细胞可以长时间记忆与抗原的接触,并在再次免疫中迅速做出应答

耶鲁公开课 - 生物医学工程探索课程节选

It's not just that your whole immune system gets revved up and it's going to respond more rapidly to any antigen it's exposed to.

并不是整个免疫系统都得以加强,免疫应答会对,以前接触过的抗原做出的应答更加迅速

耶鲁公开课 - 生物医学工程探索课程节选

So, every time you're exposed to a new vaccine or a new antigen you go through this primary response before you have the secondary response.

所以,每当你接触到新疫苗或是新抗原,在再次免疫之前,机体将会经历这样的初次免疫过程

耶鲁公开课 - 生物医学工程探索课程节选