How The Immune System ACTUALLY Works – IMMUNE · Kurzgesagt – In a Nutshell
揭秘人体免疫系统的复杂机制，了解其如何抵御病原体和癌细胞。适合练习生物相关词汇和理解复杂句子结构。
The human immune system is the most complex biological system we know, after the human brain, and yet most of us never learn how it works.
人类的免疫系统是我们所知的最复杂的生物系统之一（仅次于人脑），然而大多数人却从未真正了解它的运作原理。
Or, what it is.
或者说，事情的真相就是如此。
Your immune system consists of hundreds of tiny—and two large—organs.
你的免疫系统由数百个微小的器官以及两个较大的器官组成。
It has its own transport network spread throughout your body.
它拥有自己的运输系统，这套系统遍布你的整个身体。
Every day, it makes hundreds of billions of fresh cells organized like an army.
每天，它都会生成数千亿个新细胞，这些细胞就像一支军队一样井然有序地排列着。
With soldiers, captains, intelligence officers, heavy weapons, and crazy suicide bombers.
其中包括士兵、军官、情报人员、重型武器，以及那些疯狂的自杀式炸弹袭击者。
It's not some sort of abstract entity.
它并不是某种抽象的实体。
Your immune system is you.
你的免疫系统其实就是你自身。
Your biology protecting you from the billions of microorganisms that want to consume you, and from your own perverted cells that turn into cancer.
你的生物学机制保护着你，使你免受那些试图侵蚀你的数十亿微生物的侵害，同时也防止你体内那些发生变异、可能演变成癌细胞的细胞危害你的健康。
It's so manifold that it's impossible to cover in one video, so we'll make a series looking at different aspects of it.
这个问题涉及的内容非常广泛，根本不可能通过一个视频就全部讲清楚；因此，我们将制作一系列视频来探讨它的不同方面。
Today: What happens when your body is invaded and your first lines of defenses are engaged in a fight for life and death.
今天的话题是：当你的身体遭到入侵，而你的第一道防线开始为生死而战时，会发生什么？
It's been a normal day, when suddenly the world explodes and an asteroid rips the sky open.
原本只是平常的一天，突然间世界仿佛被炸开了锅——一颗小行星划破了天空。
Countless alien life forms invade, ready to destroy cities and infrastructure, and eat civilians...
无数外星生命体入侵地球，它们蓄意摧毁城市和基础设施，还残害无辜平民……
Or, this is what your cells experience.
或者说，这就是你的细胞所经历的过程。
You look at your bleeding thumb that you just cut on a dirty twig in the park.
你看着自己流血的拇指——刚才是在公园里被一根脏树枝划伤的。
How annoying!
真让人恼火！
But inside the wound, a horrible catastrophe has happened.
但在伤口的内部，已经发生了一场可怕的灾难。
There are dead cells, and blood and dirt everywhere.
到处都是死细胞，还有血液和污垢。
Even worse, countless bacteria invade the warm caverns between your helpless cells to explore their new home, steal your resources,
更糟糕的是，无数细菌会侵入你那些“无助”的细胞之间的温暖空间（即细胞之间的空隙），在那里“探索”这个新的“家园”，并窃取你的营养物质（即你的资源）。
and poop everywhere.
还在到处拉屎。
Immediately, the first stage of your defense kicks in.
立刻，你的防御机制的第一阶段就开始发挥作用了。
The cells that survive the impact, or are hurt or dying, scream in panic releasing an onslaught of chemical alarm signals that awaken your immune system.
那些在撞击中幸存下来的细胞，或是受到损伤、正在死亡的细胞，会惊慌失措地释放出大量化学信号，这些信号会激活你的免疫系统。
The first cells to show up are macrophages.
最早出现的细胞是巨噬细胞。
If an average cell were the size of a human, a macrophage would be the size of a black rhino.
如果一个普通细胞的体积相当于一个人的体积，那么一个巨噬细胞的体积就相当于一头黑犀牛的体积了。
A stoic cell in principle but you wouldn't want to annoy it.
从原理上讲，这应该是一个“斯多葛式”的细胞（即一种遵循某种严格规则的细胞结构）；不过你最好别去惹它……
Bacteria -do- annoy them.
细菌确实让他们感到烦恼。
Within seconds, the large cells attack and begin killing them without mercy.
几秒钟内，那些大型细胞就开始攻击并无情地杀死这些细胞。
They stretch out parts like the arms of an octopus, and grab the bacteria to swallow them whole and digest them alive.
它们会伸出类似章鱼触手的结构，抓住细菌后将其整个吞下并在体内将其消化。
A macrophage can eat 100 bacteria before it's exhausted.
一个巨噬细胞在耗尽能量之前，可以吞噬多达 100 个细菌。
But there are too many enemies, so the macrophages call for reinforcements.
但是敌人的数量实在太多，因此巨噬细胞请求增援。
In your blood, hundreds of thousands of neutrophils pick up their signals and move to the battlefield.
在你的血液中，有数十万中性粒细胞接收到信号后，会前往“战场”（即需要它们发挥作用的地方）。
Neutrophils are intense suicide warriors that only live to kill.
中性粒细胞堪称“自杀式战士”：它们的存在唯一目的就是杀死病原体。
They're so enthusiastic about killing that they
他们对杀戮行为充满了极大的热情……
kill themselves a few days after birth, so they don't have time to accidentally destroy your body from the inside.
它们在出生几天后就会自杀，这样就不会有时间从内部意外地破坏你的身体了。
As soon as neutrophils arrive, they begin vomiting deadly chemicals at bacteria, or devour them.
当中性粒细胞到达目标部位后，它们会立即向细菌释放致命的化学物质，或者直接吞噬这些细菌。
They are so careless in their attacks that they are causing real damage to your own cells.
他们在发动攻击时极其粗心大意，结果反而对你的自身细胞造成了严重的伤害。
But collateral damage is not their concern now, or ever.
但是，附带产生的损害目前（以及将来）都并非他们所关心的问题。
Some neutrophils go so far to push
有些中性粒细胞甚至会采取极端措施（即“推到极致”）。
their suicide button and explode, casting a wide and toxic net made from their own DNA filled with deadly chemicals that trap and kill bacteria.
他们按下所谓的“自杀按钮”，从而引发爆炸。爆炸产生的物质会形成一张由他们自身DNA构成的、带有致命化学物质的巨大“网”；这张“网”能够捕捉并杀死细菌。
Sometimes, they can continue fighting after that, even though they're sort of dead already.
有时候，即使他们已经“死”了（或者说已经失去了战斗能力），他们仍会继续战斗。