Each of these cells has its origins deep in your bones.

這些細胞的產生都起源於你骨骼的深處。

Bones might seem rock-solid, but they're actually quite porous inside.

骨骼似乎堅若磐石，但其實內部充滿孔洞的。

Large and small blood vessels enter through these holes.

大小血管通過這些孔洞。

And inside most of the large bones of your skeleton is a hollow core filled with soft bone marrow.

而你骨架上較大根骨頭的內部是一個空洞充滿著軟骨髓。

Marrow contains fat and other supportive tissue, but its most essential elements are blood stem cells.

骨髓含有脂肪與其他支援組織，但最重要的要素是「血球幹細胞」。

These stem cells are constantly dividing.

這些幹細胞不斷在分化。

They can differentiate into red blood cells, white blood cells, and platelets.

他們可以分化成紅血球、白血球與血小板。

And send about hundreds of billions of new blood cells into circulation every day.

然後每天將數以百計的新血球們送入血液循環系統中。

These new cells enter the bloodstream through holes in small capillaries in the marrow.

這些新細胞通過骨髓中毛細血管的孔洞進入血液。

Through the capillaries, they reach larger blood vessels and exit the bone.

透過毛細血管，他們進入更大的血管並離開骨骼。

If there's a problem with your blood, there's a good chance it can be traced back to the bone marrow.

如果你的血液有問題，有很大的機會是因骨髓造成的。

Blood cancers often begin with genetic mutations in the stem cells.

血癌經常是因為幹細胞的基因突變而引起。

The stem cells themselves are not cancerous, but these mutations can interfere with the process of differentiation and result in malignant blood cells.

幹細胞本身不具致癌性，但這些突變會干擾血球分化導致生成惡性血球細胞。

So for patients with advanced blood cancers like leukemia and lymphoma, the best chance for a cure is often an allogeneic bone marrow transplant, which replaces the patient's bone marrow with a donor's.

所以較為嚴重的血癌如白血病與淋巴癌患者，恢復機率最高的治療方法是異體血幹細胞移植，用捐贈者的骨髓置換病患的骨隨。

Here's how it works:

原理如下：

First, blood stem cells are extracted from the donor.

首先，血幹細胞從捐贈者分離出來。

Most commonly, blood stem cells are filtered out of the donor's bloodstream by circulating the blood through a machine that separates it into different components.

最常見取得幹細胞的方法是將捐贈者的血液導入儀器後，血液在儀器中循環由並將不同組成細胞分離出來。

In other cases, the marrow is extracted directly from a bone in the hip, the iliac crest, with a needle.

就其他案例來說，骨髓透過針筒直接從骨盆（骼骨）中取出。

Meanwhile, the recipient prepares for the transplant.

而取出骨髓的同時，待贈者準備接受移植。

High doses of chemotherapy or radiation kill the patient's existing marrow, destroying both malignant cells and blood stem cells.

高劑量的化療藥劑或放射線會殺死病患現有的骨髓，同時殺死惡性血球細胞與血幹細胞。

This also weakens the immune system, making it less likely to attack the transplanted cells.

這也使病患免疫系統衰弱，降低其攻擊移植細胞的機會。

Then the donor cells are infused into the patient's body through a central line.

然後捐贈者的細胞在中心血管混合入病患的身體。

They initially circulate in the recipient's peripheral bloodstream, but molecules on the stem cells, called chemokines, act as homing devices and quickly traffic them back to the marrow.

這些細胞起初在待贈者的週邊血管循環，但幹細胞上面稱為「趨化因子」的分子會作為導航歸位機制，快速的將幹細胞帶回骨髓。

Over the course of a few weeks, they begin to multiply and start producing new, healthy blood cells.

在幾個禮拜之後，他們會開始複製並生成新的健康的血球細胞。

Just a small population of blood stem cells can regenerate a whole body's worth of healthy marrow.

只要少量的血幹細胞可以重新生成供給全身使用的健康骨髓。

A bone marrow transplant can also lead to something called "graft-versus-tumor activity", when new immune cells generated by the donated marrow can wipe out cancer cells the recipient's original immune system couldn't.

骨髓移植也可以導致稱為「移植物抗癌症反應」，捐贈者的骨髓生成的新免疫細胞抹殺病患原免疫系統無法殺死癌症細胞。

This phenomenon can help eradicate stubborn blood cancers.

這個現象可以幫助根除頑固的血癌。

But bone marrow transplants also come with risks, including "graft-versus-host disease".

但移植骨髓也伴隨風險，包括「移植物抗宿主疾病」。

It happens when the immune system generated by the donor cells attacks the patient's organs.

他是指由捐贈者幹細胞生成的免疫系統攻擊宿主的器官時發生的現象。

This life-threatening condition occurs in about 30–50 percent of patients who receive donor cells from anyone other than an identical twin, particularly when the stem cells are collected from the blood as opposed to the bone marrow.

百分之三十到五十接受異體細胞而非同卵雙胞胎細胞移植的病患會發生這個危及生命的情況，特別是由血液中而非骨髓取出的幹細胞。

Patients may take immunosuppressant medications or certain immune cells may be removed from the donated sample in order to reduce the risk of graft-versus-host disease.

病患需要接受免疫抑制劑治療，或移除捐贈者細胞樣本中的特定免疫細胞，以降低移植物抗宿主疾病的風險。

But even if a patient avoids graft-versus-host disease, their immune system may reject the donor cells.

但就算病患能避免移植物抗宿主疾病，他們的免疫系統也可能拒絕接受移植細胞。

So it's crucial to find the best match possible in the first place.

所以在第一時間找到最佳搭配是很重要的。

Key regions of the genetic code determine how the immune system identifies foreign cells.

遺傳序列上有關鍵的區域去決定免疫系統如何辨別外來細胞。

If these regions are similar in the donor and the recipient, the recipient's immune system is more likely to accept the donor cells.

如果捐贈者與待贈者這些區域類似，待贈者的免疫細胞就更有可能接受移植細胞。

Because these genes are inherited, the best matches are often siblings.

因為這些基因是遺傳來的，所以最佳組合通常來自於親戚。

But many patients who need a bone marrow transplant don't have a matched family member.

但許多需要骨髓移植的病患沒有能適當搭配的家人。

Those patients turn to donor registries of volunteers willing to offer their bone marrow.

這些病患轉而向有人自願提供自己骨髓的捐贈登記處求助。

All it takes to be on the registry is a cheek swab to test for a genetic match.

需要做來成功登記的事是一個口腔內膜試驗來得知基因匹配度。

And in many cases, the donation itself isn't much more complicated than giving blood.

就許多案例而言，捐增本身比不比捐血複雜。

It's a way to save someone's life with a resource that's completely renewable.

這是可以用完全可再生的資源幫助一個人生活的方式。

If you'd like to join a bone marrow registry you can visit www.bethematch.org to get started, or to find a list of affiliated registries around the world.

如果你想要申請加入骨髓捐獻，可以前往網站 www.bethematch.org，或者查詢世界各地可以捐贈骨髓的地點。