Blood not so simple.

血液不简单。

Red cells made in a laboratory have been infused into people.

实验室人造红细胞已被输入人体。

Until the 1940s, blood transfusions often went wrong because some of the main blood-group systems, such as the Rhesus factor, had yet to be discovered.

20世纪40年代之前，输血经常出现问题，因为一些主要的血型系统，如恒河猴因子（Rh因子），还没有被发现。

This hit or miss approach to matching donors with recipients is now a thing of the past, as tests for all sorts of characteristics of an individual's blood have become available.

而现在，捐献者和接受者只能随机配对的时代已经成为过去，有很多方法可以用来测试个人血液的特征。

But finding a well-matched donor can still be difficult.

但寻找血型匹配的捐献者仍然是件难事。

Some patients have blood types so rare that there may be but a handful of appropriate donors in the country where they live.

一些患者的血型过于罕见，他们所在的国家可能只有少数合适的捐赠者。

On November 7th a consortium of researchers at several British institutions, co-ordinated by NHS Blood and Transplant, a government health authority, and Bristol University, announced a step towards solving this problem.

11月7日，一个由英国几个机构的研究人员组成的联盟，在政府卫生机构，即英国国民保健制度血液与移植中心和布里斯托大学的协调下，宣布了一项能够解决这一难题的方案。

They have successfully transfused into two healthy volunteers red blood cells grown from appropriate stem cells donated by others.

他们已经成功培养了捐献者捐献的干细胞，并将从中收获的红细胞输入到两名健康的志愿者体内。

Until now, such manufactured red cells had been given only to those whose own stem cells had been the source.

在此之前，这种干细胞培养的人造红细胞只能用于给提供干细胞的人输血。

The stem cells used for this experiment, however, were extracted from blood donated in the normal way.

然而，这项实验中用到的干细胞是从正常方式捐献的血液中提取的。

The researchers mixed into this donated blood magnetic beads armed with proteins that stick specifically to the stem cells in question, binding them to the bead.

研究人员在捐献的血液中混入磁珠，这些磁珠携带的蛋白质能够粘在有问题的干细胞上，从而将这些干细胞与磁珠连结在一起。

The beads, replete with their cellular cargo, are then easily collected.

而满载干细胞的磁珠能够轻松回收。

That done, the harvested stem cells were grown and multiplied in a nutrient solution for between 18 and 21 days, which served to turn them into young versions of red blood cells known as reticulocytes.

完成这一步筛选后，收获的合格干细胞将在营养液中生长繁殖18至21天，分化为尚未完全成熟的红细胞，即网织红细胞。

Once transfused, reticulocytes quickly develop into the real McCoy.

一旦完成输血，网织红细胞很快就会发育成真正的红细胞。

This approach would increase the value of batches of rare blood - which could, once plundered of stem cells, also be used in the normal way.

这种方法将提高大批稀有血液的价值，即使没有匹配的干细胞，也可以通过输入人造红细胞让血液维持运转。

Moreover, being newly minted, lab-made red blood cells would be expected to last longer in a recipient's body than those from a normal transfusion, since transfused blood inevitably contains a fair proportion of cells that are on their last legs.

此外，与普通血液相比，预计实验室新制造的红细胞在接受者体内存活的时间更长，因为普通血液中一定会含有一定比例快要死亡的红细胞。