How does your immune system work? - Emma Bryce

譯者: Regina Chu 審譯者: Marssi Draw

A mosquito lands on your arm,

一隻蚊子停在你的手臂上

injects its chemicals into your skin, and begins to feed.

把化學物質注入你的皮膚 並開始飽餐一頓

You wouldn’t even know it was there, if not for the red lump that appears,

你根本不知道到它曾在那裡 要不是有個包出現

accompanied by a telltale itch.

還有那洩露天機的癢癢癢

It’s a nuisance, but that bump is an important signal

那真的煩死人

可是那塊腫包是很重要的信號

that you’re protected by your immune system,

說明你已經受免疫系統保護

your body’s major safeguard against infection, illness, and disease.

它是你身體最主要的防衛 使你免受感染、微恙和疾病所苦

This system is a vast network of cells, tissues, and organs

這個系統是由細胞、組織 及器官組成的巨大網路

that coordinate your body’s defenses against any threats to your health.

協調身體的防禦工作 對抗任何對健康的威脅

Without it, you’d be exposed to billions of bacteria, viruses, and toxins

沒有它，你就會暴露在 數不清的細菌、病毒和毒物之下

that could make something as minor as a paper cut or a seasonal cold fatal.

連小小的紙割傷 或季節性的感冒都會致命

The immune system relies on millions of defensive white blood cells,

免疫系統仰賴數百萬的 防禦性白血細胞

also known as leukocytes,

又稱白血球

that originate in our bone marrow.

由我們的骨髓製造

These cells migrate into the bloodstream and the lymphatic system,

這些細胞進入血液及淋巴系統

a network of vessels which helps clear bodily toxins and waste.

即清除身體毒素和廢物的網路

Our bodies are teeming with leukocytes:

我們的身體充滿了白血球

there are between 4,000 and 11,000 in every microliter of blood.

每微升血液中就有四千到一萬一千個

As they move around, leukocytes work like security personnel,

白血球四處移動 就像身體的保安人員一樣

constantly screening the blood, tissues, and organs for suspicious signs.

隨時在看血液、組織及器官裡 有沒有可疑的徵兆

This system mainly relies on cues called antigens.

這個系統主要靠抗原提供線索

These molecular traces on the surface of pathogens and other foreign substances

這些分子附在病原體 及其它外來物質的表面

betray the presence of invaders.

出賣了入侵者的行蹤

As soon as the leukocytes detect them,

一旦白血球偵測到它們

it takes only minutes for the body’s protective immune response to kick in.

只要幾分鐘就會啟動 體內的防禦免疫反應

Threats to our bodies are hugely variable,

可以對身體造成威脅的東西非常多種

so the immune response has to be equally adaptable.

所以免疫系統也必須具備各種防禦法

That means relying on many different types of leukocytes

這意味著必須要靠各種白血球

to tackle threats in different ways.

來對付不同的威脅

Despite this diversity, we classify leukocytes in two main cellular groups,

儘管白血球種類繁多

我們還是可以將其分成兩大細胞組群

which coordinate a two-pronged attack.

協調雙管齊下的戰爭

First, phagocytes trigger the immune response

首先，吞噬細胞引發免疫反應

by sending macrophages and dendritic cells into the blood.

將巨噬細胞及樹狀細胞送進血液中

As these circulate, they destroy any foreign cells they encounter,

它們隨著血液循環 消滅任何碰到的外來細胞

simply by consuming them.

把它們吃掉，就這麼簡單

That allows phagocytes to identify

這讓吞噬細胞能辨認

the antigen on the invaders they just ingested

它們剛剛吃下的入侵者抗原

and transmit this information to the second major cell group

並把這些資訊傳送給第二種細胞組群

orchestrating the defense,

這組細胞精心策劃防禦戰

the lymphocytes.

它們就是淋巴細胞

A group of lymphocyte cells called T-cells go in search of infected body cells

有一群淋巴細胞稱為 T 細胞 它們會尋找受到感染的細胞

and swiftly kill them off.

並快速殺掉它們

Meanwhile, B-cells and helper T-cells

同時，B 細胞及輔助 T 細胞

use the information gathered from the unique antigens

會用從特異抗原得到的資訊

to start producing special proteins called antibodies.

開始製造稱為抗體的特殊蛋白質

This is the pièce de résistance:

這才是主要部分

Each antigen has a unique, matching antibody that can latch onto it

每一種抗原都有 獨特對應的抗體能與之結合

like a lock and key,

就像鎖和鑰匙

and destroy the invading cells.

並摧毀入侵的細胞

B-cells can produce millions of these,

B 細胞能製造數百萬個抗體

which then cycle through the body and attack the invaders

在體內循環並攻擊入侵者

until the worst of the threat is neutralized.

直到最糟糕的威脅被中和為止

While all of this is going on, familiar symptoms,

這些在進行的同時

熟悉的症狀像發高燒及發腫

like high temperatures and swelling,

are actually processes designed to aid the immune response.

正是設計來幫助免疫反應的過程

A warmer body makes it harder for bacteria and viruses to reproduce and spread

溫熱的身體讓細菌及病毒 難以繁衍及傳播

because they’re temperature-sensitive.

因為它們對溫度敏感

And when body cells are damaged,

而且當身體的細胞受損

they release chemicals that make fluid leak into the surrounding tissues,

會釋放出化學物質 讓液體滲出到附近的組織

causing swelling.

造成腫脹

That also attracts phagocytes,

那也會吸引吞噬細胞

which consume the invaders and the damaged cells.

吃掉入侵者及受損細胞

Usually, an immune response will eradicate a threat within a few days.

免疫反應通常會在幾天內消滅威脅

It won’t always stop you from getting ill, but that’s not its purpose.

它不一定會讓你免於疾病 但那也不是它本來的目的

Its actual job is to stop a threat

它真正的工作是停止威脅

from escalating to dangerous levels inside your body.

不讓體內的危險程度升高

And through constant surveillance over time,

透過時時監控

the immune system provides another benefit:

免疫系統還提供另一個好處

it helps us develop long-term immunity.

它幫助我們發展長期免疫力

When B- and T-cells identify antigens,

當 B 細胞與 T 細胞鑑定出抗原

they can use that information to recognize invaders in the future.

它們會用那筆資訊在未來辨識入侵者

So, when a threat revisits, the cells can swiftly deploy the right antibodies

所以，當威脅者再度入侵 細胞可以快速派出正確的抗體

to tackle it before it affects any more cells.

在影響更多細胞前就解決它

That’s how you can develop immunity to certain diseases, like chickenpox.

那就是你對某些疾病 發展出免疫力的方法，像水痘

It doesn’t always work so well.

不過並不是每次都這麼有用

Some people have autoimmune diseases,

有些人有自體免疫疾病

which trick the immune system

會欺騙免疫系統

into attacking the body’s own perfectly healthy cells.

攻擊自己體內健康無恙的細胞

No one knows exactly what causes them,

沒有人知道到底是什麼原因 造成這樣的現象

but these disorders sabotage the immune system to varying degrees,

但是這些失調會 破壞免疫系統到各種程度

and underlie problems like arthritis,

並造成潛在問題像關節炎

Type I diabetes,

第一型糖尿病

and multiple sclerosis.

及多發性硬化症

For most individuals, however,

然而，對大多數人而言

a healthy immune system will successfully fight off an estimated 300 colds

健康的免疫系統可以在一生中 成功抵擋約 300 次感冒

and innumerable other potential infections over the course of a lifetime.

及無數其他可能的感染

Without it, those threats would escalate into something far more dangerous.

沒有它，這些威脅會升級變得更危險

So the next time you catch a cold or scratch a mosquito bite,

所以下次你感冒或被蚊子叮而抓癢

think of the immune system.

想想免疫系統

We owe it our lives.

我們欠它一輩子啊