If you've lost a lot of blood, getting a transfusion of the wrong stuff can be deadly.

如果你失血過多，如果輸進錯誤血型的血可能會死亡。

But did you know that whether you're A, B, AB, or O can also put you at higher risk for things like malaria, cholera, and heart disease?

但你知道你的血型，不論是 A、B、AB 或 O 型，可能會使你有較高機率得到某些疾病，例如瘧疾、霍亂或者心臟病嗎？

The blood type you have is the result of a specific kind of antigen—in this case, a type of sugar—on the surface of your red blood cells.

之所以血型會有區別是在於紅血球表面的一種特定的抗原，而在這種情況下這些抗原是某種醣類。

If you have the A antigen, you're type A; if you have the B antigen, you're B.

如果紅血球表面有 A 型抗原，你就是 A 型血，而如果你有 B 型抗原，你就是 B 型。

If you have both, you're AB, and if you have neither, you're O.

如果你兩種抗原都有，你就是 AB 型，而如果你兩者都沒有，你就是 O 型。

But here's the thing: There's more to your blood's alphabet soup than just those three letters.

但重點來了，其實血型不僅僅局限於這三個字母。

You also have another kind of antigen—one you've probably never heard of: the H antigen.

你也擁有另一種抗原，一種你或許從來沒聽過的：H 抗原。

The A and B that you always hear about are really extra sugars that get added to antigen H.

你最常聽到的 A 還有 B 其實是某種額外附加在 H 抗原上的醣類。

And what's more, all of these sugars aren't just on your red blood cells.

更重要的是，這些醣類不僅僅在你的紅血球上。

They also appear in your guts, and in other compounds that are swimming around in your blood, where they interact with pathogens and toxins and even parts of your own immune system, to make you either more or less vulnerable to certain infectious diseases.

他們也會在你的內臟中或者其他在你血液中悠游的分子上面出現，而過程中這些醣類會與病原體、毒素甚至是你自己的免疫系統互動，使你在面對某些感染性疾病時免疫力有或多或少地提升。

For example, it turns out that having type O blood can help you, if you contract malaria.

舉例來說，如果你感染了瘧疾，O 型血可能可以幫助到你。

One of the big dangers of malaria is when your red blood cells begin to clump together, forming characteristic flower-shaped patterns known as rosettes.

瘧疾帶來最大的危害是，你的紅血球會聚集在一起，形成一個具有代表性的類似於花朵狀，而這個結構稱之為「玫瑰花結」。

They form when an infected red blood cell sticks to uninfected red blood cells—a process that's helped along by A and B antigens.

它們在一個受瘧疾感染的紅血球黏合上其他未感染的紅血球時形成，而這個過程需要有 A 抗原與 B 抗原的幫助。

As a result, people with A, or B, or AB blood tend to develop more and bigger rosettes if they get malaria.

因此，擁有 A、B、AB 型血型的人在感染瘧疾時，血液中較易生成較多較大的玫瑰花結。

These cell clusters can get lodged in tiny blood vessels—often in your brain—and block blood flow.

這些細胞叢可能阻塞微血管，且通常發生在腦部並堵塞血流。

Which is bad enough.

這個情況已經很糟了。

But when rosettes get tucked away like this, it also prevents the infected cells from being cleaned up by your body's natural defenses.

但當玫瑰花結像這樣隱藏起來時，它也使受感染的紅血球免於被人體自然的防禦機制排除。

All of this means that people with A or B or AB blood are at higher risk for a severe case of malaria than people with type O.

以上這些都意味著，擁有 A、B 或 AB 血型的人比起 O 型血的人，有較高風險染上重症瘧疾。

But, type O blood has its downsides, too.

但是，O 型血也是有缺點的。

You may fare better with malaria if you're an O, but you'll probably do worse against certain strains of the bacteria that cause cholera.

在瘧疾這方面有 O 型血的或許你可以過得不錯，但在面對會造成霍亂的某些特定細菌族群時，你可能會過得比較慘。

During an outbreak of cholera in Peru in the early 90s, people with type O blood were 8 times more likely to be hospitalized.

90 年代初期秘魯爆發霍亂疫情， O 型的人住院的可能性比其他人高出 8 倍。

And it turns out that type O blood is least common in places like the Ganges River Delta, where cholera has been making people sick for centuries.

且事實證明，O 型血在恆河三角洲地區最不常見，而霍亂在此地區也肆虐長達數百年之久。

While scientists still don't fully understand what's going on here, one idea is that having A or B antigens might help prevent the cholera toxin from binding as firmly to some of your cells.

雖然科學家們還沒有完全了解其中機制為何，但有一個想法是，A 或 B 抗原或許會幫忙阻止霍亂毒素與其他細胞緊密結合。

But this protection doesn't take place in your blood.

但這個保護機制並不在你的血液中進行。

Instead, it's the result of antigens on the cells that line your intestines.

而是發生腸內細胞上的抗原。

That's where the cholera toxin does its work, making your cells pump out water and electrolytes, and causing the diarrhea that makes cholera such a fast killer.

因為那裡才是霍亂毒素作用的地方，霍亂毒素會使你的細胞脫水與排出電解質引起嚴重腹瀉，而這也使霍亂成為一位能快速致人於死地的殺手。

For people who have As and Bs on these cells, the cholera toxin can still bind to them.

血球上有 A 抗原或 B 抗原的人，霍亂毒素仍可以與他們結合。

But it binds even more strongly to the H antigen.

但毒素會更傾向於與 H 抗原結合。

And since H is the antigen that Type O people have, Os are at greater risk for a more severe case of cholera.

而因為 H 抗原是 O 型血的人所擁有的，O 型的人會有更高的風險得到重症霍亂。

Finally, the antigens that determine your blood type can also affect your risk for heart disease.

最後一點，這些決定你血型的抗原會影響到你得心臟病的機率。

Here, it is the antigens in your blood that call the shots.

在這個情況，的確是你血液中的抗原引起的。

But not the ones on your red blood cells.

但不是那些在你紅血球上的抗原。

Instead, the key is the antigens on something called your von Willebrand factor.

事實上，關鍵是在一個叫溫韋伯氏因子上的抗原。

It sounds like the name of a German technopop band.

它聽起來很像德國電音流行樂團的名字。

But von Willebrand factor is a protein that helps your blood form clots.

但溫韋伯氏因子是一種能幫助血液凝結的蛋白質。

Obviously, you want to have enough von Willebrand factor in your blood to stop bleeding in case of an injury.

很顯然地，你會希望有足夠的溫韋伯氏因子來幫助你受傷時止血。

But having too much of it in your circulation can create clots in places you don't want, and trigger a heart attack, or a stroke.

但如果在血液循環中有太多這個因子，它會在你不需要凝血的地方凝血，因此引發心臟病或者中風。

Thankfully, your body routinely sweeps out some of this factor.

幸好，你的身體會定期清除一些這個因子。

Scientists haven't quite figured it out yet but for some reason if your von Willebrand factor has either the A or B antigens on them, that clearance is harder to do.

科學家們還沒有完全瞭解，但因為某些原因，如果你的溫韋伯氏因子上有抗原 A 或 B，排除的動作會比較難進行。

As a result, people with type A, B or AB blood have about 25 percent more of this clotting factor in their blood.

因此，A、B 或 AB 血型的人血液中溫韋伯氏因子的含量比起 O 型的人高出百分之 25。

This may explain why researchers have consistently found higher rates of heart disease, heart attack, and stroke in people with A, B, or AB blood, compared to those with O.

這也解釋了為什麼研究人員持續發現 A、B 或 AB 血型的人與 O 型的人比較起來，有較高的機率得到心血管疾病、心臟病或中風。

Now, in the grand scheme of things, your blood type is only a bit player when it comes to what diseases you might get.

就宏觀來說，你的血型只會些微影響到你會得到怎樣的疾病。

Eating too many hamburgers and not working out, for instance, are almost certainly more damaging to your heart than having A or B antigens on your blood cells.

舉例來說，比起血球上有沒有 A 或 B抗原，吃太多漢堡和沒有運動習慣才是更有可能對你的心臟造成傷害的原因。

But scientists hope to figure out why certain blood types help protect you from certain conditions, while making others worse.

但是科學家希望可以了解為什麼特定血型會幫助你免於某些危機，但在其他情況時卻會讓狀態變得更糟。

The hope is that, one day, everyone will be able benefit, whether you're an A, B, AB, or an O.

希望在未來的某一天，任何人不論 A、B、AB 抑或是 O 型的人都能受益。

Thanks for watching this episode of SciShow, which was brought to you by our patrons on Patreon.

謝謝收看本集的 SciShow，由我們在 Patreon 上的贊助者呈現給您。

If you want to help support this show, just go to patreon.com/scishow.

如果你想幫忙支持本節目，請前往 patreon.com/scishow 網站。

And don't forget to go to youtube.com/scishow and subscribe!

還有不要忘了訂閱我們頻道！