Donor DNA May Identify Early Heart Transplant Rejection

Scientists are reporting a new way to identify when a heart transplant recipient¹ is starting to reject the new organ. The new technique could help doctors ensure the success of more transplants.
The human immune system is programmed to reject foreign bodies. It's how we fight off infections. That's one of the biggest obstacles in organ transplant: the body sees the new organ as foreign.
So transplant recipients² take powerful immunosupressant drugs, but rejection³ still happens. If discovered early enough, doctors may be able to adjust the patient's medications. If not, they may need another transplant...assuming an organ is available.
To monitor for rejection of heart transplants, doctors examine the new heart for signs of rejection every couple of months.
"The current gold standard to look for rejection is to actually physically⁴ biopsy the heart, which means the doctors go in and rip a piece of it out and look at it under a microscope," says Stanford University researcher Stephen Quake, who calls the procedure "rather medieval."
"The key insight for this work was to realize that a heart transplant is really a genome transplant. When someone else's heart gets put inside your body, all the cells in that organ have that person's genome, which is different than yours. And so, if you sequence DNA⁵ from the blood, you can tell which DNA is coming specifically from the heart as opposed to other organs by those small differences in the genome."
Scientists have long known that the blood contains bits of DNA, which were in cells that have since died. And if a transplanted heart is being rejected, it will have more dead cells, and shed more DNA.
"When the organ is being rejected, your immune system is attacking it and the cells become very unhealthy and start to die, and when they die they spill their genome into the blood," Quake explains. "And so you'd expect an increase in the amount of heart DNA in the blood to be a direct consequence of damage to the heart. And that's, in fact, what we showed in this paper."
For this research, Quake studied heart transplant patients, but he says he believes the same method could be used for other kinds of organ transplants, too. That would give doctors a non-invasive, early warning of organ rejection, which can be controlled in many cases by adjusting the patient's anti-rejection medications.
The Stanford University researcher describes the DNA-based method of identifying organ rejection online in the Proceedings⁶ of the National Academy of Sciences.

1 recipient   

a.接受的,感受性强的 n.接受者,感受者,容器

参考例句：

• Please check that you have a valid email certificate for each recipient. 请检查是否对每个接收者都有有效的电子邮件证书。
• Colombia is the biggest U . S aid recipient in Latin America. 哥伦比亚是美国在拉丁美洲最大的援助对象。

2 recipients   

adj.接受的；受领的；容纳的；愿意接受的n.收件人；接受者；受领者；接受器

参考例句：

• The recipients of the prizes had their names printed in the paper. 获奖者的姓名登在报上。 来自《简明英汉词典》
• The recipients of prizes had their names printed in the paper. 获奖者名单登在报上。 来自《现代英汉综合大词典》

3 rejection   

n.拒绝，被拒，抛弃，被弃

参考例句：

• He decided not to approach her for fear of rejection.他因怕遭拒绝决定不再去找她。
• The rejection plunged her into the dark depths of despair.遭到拒绝使她陷入了绝望的深渊。

4 physically   

adj.物质上，体格上，身体上，按自然规律

参考例句：

• He was out of sorts physically,as well as disordered mentally.他浑身不舒服，心绪也很乱。
• Every time I think about it I feel physically sick.一想起那件事我就感到极恶心。

5 DNA   

(缩)deoxyribonucleic acid 脱氧核糖核酸

参考例句：

• DNA is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。
• Gene mutations are alterations in the DNA code.基因突变是指DNA密码的改变。

6 proceedings   

n.进程，过程，议程；诉讼(程序)；公报

参考例句：

• He was released on bail pending committal proceedings. 他交保获释正在候审。
• to initiate legal proceedings against sb 对某人提起诉讼