that B-cells - a particular subset of B-cells - gets activated.

B细胞一类特别的B细胞亚族被激活
What happens when they're activated is they start to reproduce,

激活后免疫细胞开始增殖
they make more and more, and more B-cells.

B细胞变得越来越多
Those B-cells also mature,

这些B细胞也会变成熟
they differentiate and that's what's shown on this slide here

并且进行分化这都展示在幻灯片上了
is the differentiation of those immature B-cells into mature B-cells.

未成熟的B细胞分化为成熟的B细胞
What do immature B-cells do?

未成熟的B细胞都在做什么呢
They just wait,

它们时刻准备着
they wait for their time,

在等待着那一刻
they wait until you are in danger from a particular antigen.

等待你被某种特别的抗原威胁的时刻
When you get exposed to that particular antigen they say,

等到你暴露在特定的抗原中它们说
'I'm on,

该我了