The two main kinds of antigens, A and B, determine your blood type.

不会误以为是外， 而加以攻击。

Her body was fighting a foreign invader, and she wasn't getting any help.

她的身体在抗击一种外的入侵，而没有人给她任何帮助。

In many cases, train workers have to remove foreign objects from overhead lines manually.

在大多情况下，铁路工作人员必须手动从接触网清除外。

Over the years, scientists have analysed these meteorites and determined their age through radioactive dating.

近年，科学家们分析了这些外通过放射性同位素衰减测其年龄。

And because they're part of our bodies, the liver is less likely to label them as foreign.

因为它们是我们身体的一部分，肝就更不可能会把它们当成外。

The bigger the foreign object, the harder it is to clean it up. Bird nests are one of the most difficult.

异越大，清理起就越困难，鸟巢是最难清理的外之一。

Those chemical markers can identify foreign bodies like pathogens-small organisms, such as a virus or bacteria, that can cause disease.

那些化学标记能够识别外，例如病原体——能够引发疾病的小型有机，例如病毒或细菌。

Birds eat the seeds of invasive plants and spread them to other places.

鸟类会吃掉外入侵植的种子，传播到其他地方。

The body identifies those fragments as foreign and responds by producing compounds called antibodies, tailormade to match the antigens.

身体将这些段识别为外，并通过产生称为抗体的化合做出反应，这些化合是为匹配抗原而量身定制的。