Despite anything the science of medicine may have achieved, the immune system is our main defence against disease.

不管医疗科学已取得了什么样的进步，免疫系统仍是我们抵抗疾病的主要防御手段。

《柯林斯英汉双解大词典》

The most serious deficiency in NATO's air defence is the lack of an identification system to distinguish friend from foe.

北约防空的最大缺陷就是缺乏能够辨认敌友的识别系统。

《柯林斯英汉双解大词典》

The Human Immunodeficiency Virus (HIV) targets the immune system and weakens people's surveillance and defence systems against infections and some types of cancer.

人类免疫缺陷病毒(艾滋病毒)感染免疫系统，削弱人体对感染以及一些癌症的监视和防御系统。

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Russia appears close to agreeing a deal to revise the anti-ballistic missile treaty - lifting its objections to an American system of missile defence.

BBC: Shanghai showcase

When the US embarked in the 1950s on the construction of the 42, 795-mile National System of Interstate and Defence Highways, Americans applauded.

BBC: Killer on the road: why mass murderers haunt US highways

There is also a more subtle defence of the American political system: the hazing defence.

ECONOMIST: A hard day’s night | The