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104、免疫系統
Immune System: Innate and Adaptive Immunity Explained
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Our body has a powerful army
我們體內有一支強大的軍隊
that protects it from various types of threats.
幫我們抵禦種種威脅
These threats can come in the form of mechanical injuries,
這些威脅包括機械性損傷
the entry of germs,
細菌入侵
or the entry of other foreign particles like dust.
或是異物顆粒比如灰塵進入體內
This personal army is called the immune system.
這支私人軍隊叫做免疫系統
《科學ABC》
Every day, we encounter a huge number of bacteria,
每天我們都會遇到大量細菌
viruses and other disease-causing organisms.
病毒和其他致病的生物
However, we don’t fall ill every other day.
但是 我們不會每天都生病
which is due to our immune system-
這要歸功於我們的免疫系統——
an army of cells that is always roaming our body,
一支時刻在我們體內巡邏的細胞軍隊
ready to ward off any attack.
準備抵禦任何攻擊
The immune system can be broadly divided into two parts
免疫系統大致可以分為兩部分
innate and adaptive immunity.
固有免疫和適應性免疫
Innate immunity or non-specific immunity
固有免疫 或稱非特異性免疫
is the body’s first natural defense to any intruder.
是身體對入侵者的第一道天然防線
This system doesn’t care what it’s killing.
這種免疫系統不關心消滅的是什麼
Its primary goal is to prevent any intruder from entering the body,
它的首要目標是避免任何入侵者進入體內
and if it does enter,
一旦侵入體內
then the immune system neutralize this intruder.
那麼免疫系統就會消滅入侵者
It doesn’t differentiate between one pathogen and another.
而且它不會一個一個區分病原體
The first component of this defensive system is your skin.
這個防禦系統的第一部分就是你的皮膚
Any organism trying to get into the body is stopped by the skin,
它會阻止所有試圖進入身體的生物
our largest organ, which covers us.
是我們最大的器官 覆蓋在全身
Secondly, there is the mucous lining of all our organs.
其次 我們所有器官內壁都有黏膜
The sticky, viscous fluid traps any pathogens trying to get past it.
這些黏稠的黏液會阻止試圖通過的病原體
These are the two physical barriers.
這是兩道物理屏障
However, we also have chemical barriers,
然而我們還有化學屏障
such as the lysozyme in the eyes, or the acid in the stomach,
比如眼睛裡的溶菌酶 還有胃裡的胃酸
which kill pathogens trying to gain entry.
都會消滅想要入侵的病原體
The genitourinary tract and other places
泌尿生殖道和其他地方
have their own normal flora, or microbial community.
都有自己的正常菌群 或微生物群落
These compete with pathogens for space and food,
它們與病原體爭奪空間和食物
and therefore also act as a barrier.
所以也起到了屏障的作用
The next line of defense is inflammation,
下一道防線是炎症
which is done by mast cells.
由肥大細胞引起
These cells are constantly searching for suspicious objects in the body.
這些細胞在體內不斷地搜尋可疑物
When they find something, they release a signal in the form of histamine molecules.
找到後 它們會釋放組胺分子作為信號
These alert the body,
這會讓身體警覺
and blood is rushed to the problem area.
血液會迅速聚集到有問題的區域
This causes inflammation and also brings leukocytes, or white blood cells,
這會導致炎症 還會帶來白血球 或稱白細胞
which are soldiers in our body’s cellular army.
它們是我們體內細胞軍團的士兵
Once they come, all hell breaks loose!
一旦到來 頓時亂作一團
Sometimes however, the intruder may not be germ,
但是有時入侵者可能不是細菌
but rather a harmless thing like a dust particle.
而是像灰塵之類的無害物
The body still causes a full immune reaction to this intruder,
人體還是會對它產生完全的免疫反應
which is how allergic reactions occur.
這就是產生過敏反應的原因
In the fortress of our body, the leukocytes are VIPs.
在我們的身體堡壘中 白血球是VIP
They have an all-access pass to the body,
它們擁有通往全身的權限
except, of course, to the brain and spinal cord.
當然 除了大腦和脊髓
Our leukocytes come in many types.
白血球有很多種類
Those that belong to the innate system are the phagocytes.
那些屬於固有免疫系統的是吞噬細胞
These cells can either patrol your body, like the neutrophils,
這些細胞能在體內巡邏 比如中性粒細胞
or they can stay in certain places and wait for their cue.
也能待在特定的位置等待指示
Neutrophils are the most abundant cells.
中性粒細胞是體內數量最多的吞噬細胞
They patrol the body and can therefore get to a breach site very quickly.
它們在體內巡邏 以便儘快到達傷口
These cellular soldiers kill the infectious cell and then die,
這些細胞士兵殺死感染細胞後死亡
which leads to pus formation.
這導致了膿液的形成
There are also the big bad wolves, or the macrophages.
還有一些狠角色 叫做巨噬細胞
These cells are like hungry, ravenous monsters
這些細胞就如飢餓貪婪的怪物一般
who simply engulf unwanted pathogens.
簡單粗暴地吞下有害病原體
Instead of roaming freely in our blood,
它們會在特定區域聚集
they are collected in certain places.
而不會在血液中自由巡邏
These cells can consume about 100 pathogens before they die,
這些細胞在死前可以消滅大約100個病原體
but they can also detect our own cells that have gone rogue,
但它們也可以識別病變的細胞
such as cancer cells, and kill them too.
例如癌細胞 並消滅它們
Beyond that, we also have the Natural Killer Cells.
此外 我們還有自然殺傷細胞（NKC）
These cells can efficiently detect when our own cells have gone rogue,
這些細胞可以高效地識別病變的
or are infected with, say, a virus.
或被感染的細胞 比如被病毒感染
NKCs detect a protein produced by normal cells,
NKC會識別正常細胞合成的一種蛋白質
called the Major Histocompatibility Complex or MHC.
叫做主要組織相容性複合體或MHC
Basically, whenever a cell isn’t normal,
一般來說 細胞一旦發生異常
it stops producing this protein.
就會停止合成這種蛋白質
The NKCs move around constantly,
NKC會不斷地移動
checking our cells for this type of deficiency,
來檢查細胞是否有這種蛋白質缺失
and when they find an abnormal cell,
在找到異常細胞後
they simply bind to it and release chemicals that will destroy it.
就會與之結合 並釋放化學物質將其破壞
The last cells of our innate immune system are the dendritic cells.
固有免疫中最後一類細胞是樹突狀細胞
These are found in places that come in contact with the outside environment,
它們分布於與外界環境相連通的地方
such as the nose, lungs, etc.
比如鼻子 肺等
They are the link between our innate and adaptive immune systems.
它們是固有免疫與適應性免疫系統之間的紐帶
They eat a pathogen,
它們吞噬病原體
and then carry information about it to our adaptive immune system cells.
然後給適應性免疫系統的細胞帶去相關的信息
This information is produced and shared in the form of antigens.
這個信息以抗原的形式產生並共享
Antigens are the traces that pathogens leave around.
抗原是病原體留下的痕跡
They are molecules found on the surface on pathogens
它們是位於病原體表面的分子
that can be detected by our adaptive immune system for recognition.
可以被適應性免疫系統發現以識別
The dendritic cells pass on this information to our T cells.
樹突狀細胞會把這些信息傳遞給T細胞
However, macrophages can also perform this function.
然而 巨噬細胞也能起到這個作用
Now, there is also the adaptive or acquired immune system.
此外 我們還有適應性 或稱獲得性免疫系統
This system is more efficient,
這個系統更加高效
as it can differentiate between different types of pathogens.
因為它可以分辨不同類型的病原體
It has 2 main components – T lymphocytes and B lymphocytes.
它主要有兩部分 T淋巴細胞與B淋巴細胞
T-cells come into play when an infection has already occurred,
T細胞在感染發生後才會介入
thus bringing about the cell-mediated immune response.
從而引起細胞免疫應答
B-cells join the fight when the pathogens have entered,
B細胞會在病原體進入人體
but haven’t yet caused any disease.
但還未引起疾病時介入
This is called the humoral immune response.
這被稱為體液免疫應答
Some T-cells take signals from the dendritic cells or macrophages,
有些T細胞會接收樹突狀細胞或巨噬細胞的信號
and are thus called helper T-cells.
所以也被稱為輔助T細胞
They perform two key tasks:
它有兩個關鍵任務：
forming effector T-cells, which are basically cells that cycle through the body
形成效應T細胞 在體內循環
and call in the cavalry, namely other white blood cells.
並且呼叫「騎兵」 即其他白細胞
Helper T-cells also form memory T-cells,
輔助T細胞還會形成記憶T細胞
which keep a record of this antigen for future reference.
它們會記錄下這個病原體供下次參考
Sometimes, some cells of our body know that they have lost the battle.
有時 身體的某些細胞知道自己打了敗仗
They have become heavily infected with pathogens,
它們被病原體嚴重感染了
so there is no hope for them.
所以已經沒救了
At this point, the immune system brings out the cytotoxic t cells.
此時 免疫系統會叫來細胞毒性T細胞
These cells rush over and perform a mercy killing for the infected and dying cell.
跑去給瀕死的感染細胞安樂死
Furthermore, we have the B-cells.
此外 我們還有B細胞
They produce chemicals called antibodies,
它們會產生名為抗體的化學物質
which fit on the antigens of pathogens,
抗體與病原體的抗原相結合
much like how a lock and key fit together.
就像鎖和鑰匙組合在一起
These antibodies crowd around a pathogen and act like tags,
這些抗體會在病原體上聚集 並作為標籤
They signal the macrophages to come and kill the marked pathogen.
指示巨噬細胞來殺死被標記的病原體
B-cells also produce memory B-cells when they encounter an antigen.
B細胞遇到抗原時也會產生記憶B細胞
The B- and T- memory cells jointly maintain a record of all encountered infections,
記憶B T細胞對所有遭遇過的感染都有記憶功能
and thus strengthen and solidify the body’s immune response to these infections in the future.
從而加強並穩固將來對於這些感染的免疫應答
Our innate response is quicker, though non-specific.
固有免疫應答不具有特異性 但它非常迅速
It gets into action within hours and is pretty strong.
幾小時內就能起作用 效果也很好
However, when things get out of hand,
然而 當情況失控時
the innate system calls for help from the acquired immune system.
固有免疫系統會向獲得性免疫系統尋求幫助
This system can take days to mount a response,
這個系統要花幾天才能做出應答
but the next time we encounter that pathogen,
但是下次遇到這個病原體
it won’t make us get sick.
我們就不會生病了
In short, every day that we spend being healthy
總之 我們能健康地度過每一天
is all thanks to our immune system.
都要歸功於免疫系統
So, it definitely deserves our respect.
所以它絕對值得我們尊重
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