背景介绍：
糖尿病是一种由胰岛素绝对或相对分泌不足以及利用障碍引发的，以高血糖为标志的慢性疾病，现在已经是影响人类生命最严重的疾病之一。而糖尿病最可怕之处并不是疾病本身，而是其所带来的众多并发症。不过，美国一组科研团队最近有了重大科研突破：加州大学的研究人员认为他们可能已经找到了治愈糖尿病的方法。
New treatments
are emerging for type-1 diabetes
一型糖尿病的新疗法
The trick is
to outsmart the immune system
诀窍在于骗过免疫系统
“Where are the islets of Langerhans?” is a trick
question that pops up from time to time in quizzes. The answer is to be found
not in atlases of geography, but rather in those of anatomy, for the so-called
islets are in fact clusters of cells scattered through the pancreas.
知识问答中时不时会出现这么一个刁钻问题：“朗格汉斯岛在哪里？”答案不在地理地图中，而在解剖学图册里，因为朗格汉斯岛实际上是散布在胰腺中的细胞团，也称为胰岛。
There they synthesise and release a range of hormones, including
insulin
, which regulates glucose levels and thus
metabolism
.
胰岛合成并释放多种激素，包括调节葡萄糖水平继而调节新陈代谢的胰岛素。
The islets’ insulin producers are called beta cells.
(Cell types alpha, gamma, delta and epsilon perform other tasks.) They are the
only bodily sources of that hormone. So, if their number declines, trouble
looms.
胰岛中分泌胰岛素的细胞称为 beta 细胞。（alpha、gamma、delta 和 epsilon 等其他类型的细胞执行别的任务。）它们是人体内唯一的胰岛素来源。因此，如果 beta 细胞数量减少，就会出现麻烦。
And decline it does, in the condition known as type-1 diabetes. This happens when, in a phenomenon called autoimmunity, the body’s own immune system attacks its complement of beta cells,
wiping out
as many as 80%.
而它确实会减少，患上一型糖尿病就会这样。这种糖尿病的发病是因为自身免疫现象：人体的免疫系统攻击自己的 beta 细胞，会消灭多达80%的这种细胞。
Without an alternative supply of insulin, someone with
type-1 diabetes will die. (In type-2 diabetes, insulin continues to be produced
but the body’s cells acquire resistance.)
如果没有另外的胰岛素补充，一型糖尿病患者将会死亡。（在二型糖尿病中，胰岛素仍然继续分泌，但人体细胞对其产生了抵抗。）
Supplementary insulin can be administered by injection or via a device called an insulin pump. But a better way might be to replace the missing beta cells and somehow protect them from immune attack.
可以通过注射或使用名为胰岛素泵的装置来补充胰岛素。但更好的方法也许是替换缺失的 beta 细胞，并想办法保护它们免受免疫攻击。
A few lucky patients do indeed have their beta cells
replaced—by transplantation from human donors. And Vertex Pharmaceuticals, a
firm in Boston, is testing beta cells grown from stem cells for the same
purpose. But neither approach includes immune protection.
少数幸运的患者确实通过人类供体移植替换了beta细胞。而波士顿的 Vertex Pharmaceuticals 正在测试由干细胞培养的 beta 细胞，以便能做同样的替换。但这两种方法都没有免疫保护。
This means both require the administration of immunosuppressive drugs to prevent the rejection that follows any transplant, let alone one where autoimmunity is at play.
这意味着它们都需要使用免疫抑制药物以避免排斥反应——任何移植手术后都会有排斥反应，更不用说还有自身免疫性现象在发挥影响了。
One of the sessions at this year’s meeting of the American Association for the Advancement of Science in Denver therefore looked into how transplanted beta cells might be made hypoimmunogenic—in other words, invisible to a patient’s immune system.
因此，今年在丹佛举行的美国科学促进会年会上，就有一个专场讨论如何让移植的 beta 细胞具有低免疫原性——换句话说，就是在患者的免疫系统面前隐形。
Sonja Schrepfer, who works for the University of
California, San Francisco (UCSF), and also at Seattle-based Sana Biotechnology,
proposes a twofold approach, to deal with the fact that the immune system has
two arms.
在加州大学旧金山分校和西雅图的 Sana Biotechnology 工作的索尼娅·施雷普弗提出了一种双管齐下的方法，以应对免疫系统的两个部分。
One, the adaptive arm, is the basis of tissue rejection. This adaptive arm can recognise the signature of “selfness” provided by an individual’s HLA proteins. These molecules contain so-called hypervariable regions, which differ from individual to individual.
其一是后天性免疫系统，也是组织排斥的基础。这种适应性免疫系统能够识别人体 HLA 蛋白表达的“自我”特征。这些分子包含有名为超变异区的部分，每个人都各不相同。
If the immune system comes across non-self HLA proteins, it recognises the cells displaying them as interlopers and attacks, using shock troops called killer T-cells and antibodies.
如果免疫系统遇到非自身的 HLA 蛋白，它就会将表达这种蛋白的细胞视为入侵者，并使用杀伤性T细胞和抗体作为突击部队对其发起攻击。
The first part of Dr Schrepfer’s approach is therefore
to prevent the production of HLAproteins in laboratory-grown beta
cells destined for transplant. This can be done by editing two genes involved
in their production, theoretically rendering the cells in question invisible to
the adaptive arm.
因此，施雷普弗的方法首先要避免在实验室培养的用于移植的 beta 细胞产生 HLA 蛋白。要做到这一点，可以对参与产生 HLA 蛋白的两个基因进行编辑，理论上可以让这些细胞在后天性免疫系统面前隐身。
Lack of HLA proteins does,
however, bring a cell to the attention of immunity’s other arm, the innate
system. Its troops are called NK (natural killer) cells and macrophages, and
one of the red flags it reacts to is an absence of any sort of HLA.
然而，缺少 HLA 蛋白又会引起免疫系统的另一个部分——先天性免疫系统的注意。它的部队称为自然杀伤细胞和巨噬细胞，缺乏任何一类 HLA 都是一个危险信号，会让它做出反应。
It can, however, be warded off by over-expression of a protein called CD47, something that Dr Schrepfer’s team also achieved by genetic manipulation of their beta cells.
然而，通过一种 CD47 蛋白的过度表达可以避免它的攻击，施雷普弗的团队也通过对其 beta 细胞进行基因编辑实现了这一点。
It seems to work. In an experiment whose results were
announced just before the meeting, the team first induced diabetes in a
laboratory monkey and then injected their modified beta cells into one of its
muscles. The diabetes went away, and stayed away for more than six months. Now
they have moved on to people.
这种方法似乎奏效了。在会议前不久公布的实验结果显示，研究团队首先在一只实验猴身上诱发了糖尿病，然后在它的一块肌肉中注入改造过的 beta 细胞。糖尿病消失了，而且持续了六个多月。现在，他们已经进入人体试验阶段。
insulin
[ˈɪnsəlɪn] n. 胰岛素
