modern medicine has an impressive arsenal.

現代醫學擁有許多武器

And one of its most versatile weapons

其中最靈活的武器之一

are Y-shaped proteins called monoclonal antibodies.

是一種叫「Y型蛋白質」的單株抗體

Our immune systems already produce

我們本身的免疫系統

their own antibodies.

本身就能自行製造抗體

They come in billions of variations,

這些抗體的種類多達數十億

each matching a specific target,

每種都對應著一個特定的標靶

such as a particular toxin, bacteria or virus.

比如某種毒素、細菌或病毒

When they bind to their target, they send a signal…

當它們結合到標靶上時，會發送訊號

This bacterium is now marked for destruction.

這個細菌就被貼上了「待消滅」的標誌

These naturally-produced antibodies are pretty effective,

這些自然形成的抗體效果不錯

but in the 1970s,

但是在1970年代

scientists figured out how to mass produce them.

科學家找到量產它們的辦法

They can take any specifically-targeted antibody

它們能提取出靶向特定目標的任何抗體

and make huge numbers of identical clones,

並大量製造

which means you can produce monoclonal antibodies,

也就是說人們可以製造出

for almost any disease you can think of.

幾乎任何疾病的單株抗體

Which brings us on to cancer…

這就把我們引到了癌症上

Mutated cells that start growing out of control

生長開始失控的突變細胞

can be deadly.

可能致人於死

But, the body's immune system

但是，人體的免疫系統

isn't defenceless.

並非毫無防備

Meet the CTL.

這位是CTL（毒殺型T細胞）

It's a type of white blood cell

是一種白血球

that can detect infected or mutated cells,

能偵測到被感染或發生突變的細胞

and when it finds one, it secretes toxic molecules

當它發現這種細胞，就會分泌毒素

that initiate a self-destruct sequence.

啟動自毀程序

But the CTLs do sometimes need to be reined in.

但CTL有時還是要煞個車

If they get overenthusiastic

因為它的鬥志可能會過於高昂

the immune system can start causing collateral damage

免疫系統可能會被誤傷

– attacking healthy cells.

攻擊健康的細胞

Fortunately, the CTLs can be turned off

幸運的是，活化一種叫PD1的份子

by activating a molecule called PD1.

就能夠「關掉」CTL

The trouble with having an 'off-switch'

存在這樣一個「開關」的問題

is that cancer cells can exploit it.

在於癌細胞也能夠利用它

Many cancer cells protect themselves

許多癌症細胞利用一種叫PD-L1的反受體

with a counter receptor called PD-L1.

來保護自己

This is where monoclonal antibodies come in.

這就是單株抗體該出手的時候了

Scientists can use one of two types:

科學家可以選擇兩種之一

one that binds the PD-1 molecule,

一種與PD-1份子結合

or another that goes for PD-L1.

另一種與PD-L1結合

Thanks to the monoclonal antibodies,

多虧了單株抗體

all of the CTLs are fully activated

所有CTL都被充分活化

and can blast away the cancer.

能夠殺死癌細胞

This is just one way

這只是單株抗體

that monoclonal antibodies can be used.

的眾多用處之一

They've already proven effective

事實已經證明

against a whole range of cancers

它們對多種癌症有效

and yet more are still being developed.

而更多種類還在研發中

With their ability to be targeted at specific diseases,

能夠靶向特定疾病的單株抗體

monoclonal antibodies

顛覆了醫學界

are turning out to be a game-changer,

也成了我們對抗癌症

and one of our most effective weapons

的武器中

in the fight against cancer.

相當重要的一員