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The proverbial needle in the haystack: the right stem cell donor

When two people are “matched” at the Center for Transfusion Medicine and Hemotherapy at UKGM Giessen, it is not about a dating app, it is about life and death. “We speak of a ‘match’ when the search unit has found a potential stem cell donor for a blood cancer patient,” explains Katja Müller, pointing to the computer screen in her small office. It shows two identification numbers – one for the donor and one for the patient – as well as two tables with combinations of numbers and letters. If they are identical, then two have found each other – a terminally ill person and his potential lifesaver.

Katja Müller is the medical technology assistant and head of the tissue typing laboratory, which operates an in-house bone marrow and blood stem cell donor database as well as a search unit to track down suitable stem cell donors. The trained biology laboratory assistant is looking for the proverbial needle in the haystack: in the best case, the probability of a “match” is 1: 300, in the worst case there is not a single compatible donor for a patient worldwide.

Katja Müller and her colleagues Marion Ernst-Schlegel, Christina Lang and Mirijam Weiß are nevertheless positive. Because the bone marrow donor database at the UKGM is growing steadily – and with it the chances of finding suitable donors also increase. At the moment, a donation can be made once a month on average. Around 10,000 people have registered since the file was set up in the mid-1990s. But why do you need an in-house file at all when there is the German bone marrow donation (DKMS) with more than six million registered donors?

“The tissue characteristics of our donors, like those of the DKMS, are fed into a central register,” explains Dr. Sandra Wienzek-Lischka, who heads the team of four at the bone marrow donor center and the tissue typing laboratory. “Our big advantage, however, is that we link the stem cell donor registration to the blood donation.” This means that everyone who donates blood at the UKGM is informed that they can register as a stem cell donor. “In this way, we can be sure that the donor is not afraid of needles and is already able to handle the blood donation. Anyone who only registers with a swab with a cotton swab does not know what to expect when in doubt, ”explains Wienzek-Lischka. Another plus point: Since the stem cell donors of the UKGM also give a blood sample instead of just a saliva sample, more medical data is available about them. The more data there is, the more accurately it can be predicted how well a donor will fit. This is why our file is often used.

The search

But how do you even know whether a dispenser fits? To understand this, you have to walk a few rooms further from the small office with the computer full of data: into the laboratory. Between the neon tubes and the linoleum floor, there are refrigerators and freezers of various sizes in which thousands of plastic tubes with liquids are stored: blood samples over blood samples. There are a number of technical devices on the work surfaces. One is similar to a conventional office copier, another is reminiscent of a microwave. It looks pretty unspectacular for the fact that the code of life is cracked here: the DNA. The DNA of patients and donors is analyzed for very specific features: the features on the cell surface. “You can imagine DNA like a thick book,” explains Wienzek-Lischka. “All of our individual characteristics have their own page, the hair color, the size and also the so-called HLA or tissue characteristics that describe the surface of our cells.” When donating stem cells, two people have to be found whose cell surface is as identical as possible. More precisely: ten of the ten most important tissue characteristics must match for both. “Only then is there a high probability that the body will not recognize the stem cells as foreign after the transfusion and will not start a defense reaction,” says the transfusion specialist.

But it takes a while for the team to type the tissue characteristics from a blood sample and enter the data in the donor register. The blood sample moves from device to device and is becoming increasingly small. First the DNA is isolated, then the part of the DNA on which the tissue characteristics are described is copied, processed several times and finally read out overnight. What remains is a picture: A kind of graph with ups and downs, individual places are marked with lines, the lines are labeled with combinations of the letters A, C, G, T. The “genetic fingerprint” of the tissue characteristics. It can also be shown in a table. The table that MTA Katja Müller sees on her computer during a “match”.

You can think of DNA like a thick book

“This entire process of typing is already high-speed today,” explains Marion Ernst-Schlegel. Just isolating the DNA from the blood used to take half a day, today it takes just 23 minutes. “Up until a few years ago we had to do everything by hand in dozens of steps,” says the MTA.

Finding two of the same is the said search for a needle in a haystack. It takes place at the UKGM in close cooperation with the doctors. If a patient in Giessen or Marburg needs a stem cell transplant, the search unit team receives precise information: What disease does the patient have? What is his current state like? How is the transplant planned? Every year the UKGM makes around 90 searches for donors, and across Germany there are around 10,000.

The donation

A successful search is particularly remembered by Katja Müller. Why? She had not looked for a donor, but was “matched” herself as a donor. At that time, Müller immediately agreed: “If someone has a new chance of survival through my stem cell donation, there is no turning back for me – from a moral point of view alone.” Was she afraid? Yes, but the joy of being able to help was greater. She only underestimated the preparation for the donation. For four days, the donors have to inject a so-called growth factor once or twice a day. It ensures that the bone marrow releases stem cells and releases them into the bloodstream. “I knew that pain and flu-like symptoms were normal in this phase. Nevertheless, it was a burden for me, I had the feeling that someone was sitting on my chest, ”said the 43-year-old. The donation itself, on the other hand, was child’s play. Not painful, just a little boring. For five hours, Müller was connected to the apheresis machine, a kind of washing machine that filters the stem cells from the blood. In the crook of each arm a needle with a tube, I couldn’t move. But after the donation, two valuable things remain: a bag with almost 350 milliliters of pure stem cells and a good feeling. “You give little and you can achieve a lot,” is how Müller describes it. Your “match” gave a patient precious life.

Register yourself too
as a donor for the UKGM’s bone marrow donor database! Information at:, Tel. 0641-985 41525

Your expert for transfusion medicine:

Dr. Sandra Wienzek-Lischka
Senior Physician, Center for Transfusion Medicine and Hemotherapy at the University Hospital Gießen and Marburg at the Marburg location

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