Because on second exposure there's another population of cells that I haven't mentioned before that remain after the primary exposure and those are called memory cells, they're down here.

因为在再次免疫中,有另外一些细胞,我之前并没有提到过它们,在初次免疫结束后保留下来的细胞,被称为记忆细胞,它们在下面

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So, these memory cells are a way that your immune system keeps track of antigens that it's been exposed to for even if maybe the plasma cells that were producing antibody in response to the initial exposure have died and disappeared.

所以,这些记忆细胞,是人体免疫系统记忆抗原的一种方法,即使由浆细胞产生的抗体,在初次免疫应答中全部被消灭,记忆细胞仍然能迅速分化为抗体分泌细胞

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