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

不会误以为是外来物， 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来物的入侵，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来物。

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

近来，科学家们分析了这些外来物通过放射性同位素衰减龄。

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来物。

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

异物越大，清理起来就越困难，鸟巢是最难清理的外来物之一。

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来物，例如病原体——能够引发疾病的小型有机物，例如病毒或细菌。

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

鸟类会吃掉外来入侵植物物的种子，传播到他地方。

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

身体将这些片段识别为外来物，并通过产生称为抗体的化合物做出反应，这些化合物是为匹配抗原而量身定制的。