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Stem cells suppress rejection in organ transplants

Treatment with special stem cells seems to be a good option for suppressing the immune system in organ transplants. Researchers are trying to learn from processes that take place in the human body during pregnancy.

Organ transplants are complex operations, and immunologically they are an enormous challenge, mainly because the immune system treats the donor organ as a foreign body. Ensuring a good match between donor and recipient can prevent a lot of problems in the short term. ‘We are now well able to make sure that kidneys are accepted by the body following a transplant and that they work well during the initial period. The major challenge now is the long term,’ explains Marlies Reinders, a specialist in internal medicine and nephrology. ‘Patients need a lot of drugs to suppress the immune system, but these drugs have side-effects. For example, people are more susceptible to infections and more likely to develop tumours. Not only that, the kidney can easily be damaged by scar formation. This is why we are looking for new ways of suppressing the immune system without incurring all these side-effects.’ 

Learning from pregnancy

Professor Frans Claas draws inspiration from an unexpected source. He is studying how a mother’s body treats her unborn child during pregnancy. Just like a donor organ, the foetus is a foreign body for the mother’s immune system, or at any rate that applies to half of the child’s genes. ‘You can see in the blood of a pregnant women that all kinds of antibodies have been made against the child. But somehow the child is not rejected,’ Claas explains. He wants to find out how this is possible, so that he can apply this knowledge to organ transplants. He has already discovered that during pregnancy the immune system is held in check by what are known as regulatory T-cells. ‘In our research we are trying to find out exactly how these regulatory T-cells work, and whether we can create similar conditions for organ transplants. We could do that, for example, by injecting regulatory T-cells during the transplant that we had taken from the patient beforehand.’

Stem cells as immunosuppressive drug

An alternative way of suppressing the immune system is to administer mesenchymal stromal cells (MSC). These are stem cells from bone marrow. ‘We think that the mesenchymal stromal cells ensure that there are fewer aggressive immune cells and more regulatory T-cells. This creates a much more favourable environment for an organ transplant,’ 

Reinders explains. The stem cells are removed from the patient during an operation; they’re then cultivated and later fed back via a drip. The first clinical trial to test the feasibility and safety of the stem cells gave positive results. A second trial has to be carried out to see whether patients need to use fewer immunosuppressive drugs and whether they experience fewer side-effects and less scarring as a result of this treatment.

A mesenchymal stromal cell (MSC).
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