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New discovery may end transplant rejection

 

Big news in the medical world: scientists in Australia have found a way to stop the body from attacking organ transplants, greatly decreasing the possibility of organ rejection.

 

The last major hurdle of transplantations is the body itself. When a new tissue is introduced, one's immune system kicks into overdrive, sending out cells known as killer T cells to attack and destroy the unknown tissue. Because of this, those who receive transplants have to maintain a regime of toxic immune-suppressing drugs.  Not only does that make them more likely to have severe complications from diseases the immune system would normally handle easily, the drugs themselves do not-so-nice-things to the body as a whole.  Getting past the immune system obstacle would be the medical breakthrough of the year (maybe, and sincerely, even the decade).

 

Professor Jonathan Sprent and Dr Kylie Webster from Sydney's Garvan Institute of Medical Research focused on a different type of T cells – known as regulatory T cells (Treg) – in this study.  Tregs are capable of quieting the immune system, stopping the killer T cells from seeking out and attacking foreign objects.  Usually, these cells live in basic equilibrium, allowing the killer T cells to destroy what needs to be destroyed, but stopping them once the infection is over.  The idea was to boost the number of Tregs in the system, quieting the killer T cells for a period of time sufficient for the body to accept the new tissue. After that point, the immune system would return to normal activity.

 

Using a complex that contained a molecule known as interleukin-2, a molecule that promotes T cell proliferation, the researchers radically increased the number of Tregs in healthy mice before performing the transplants, effectively quieting the killer T cells. Webster explained what followed after the transplant: "The numbers of T regulatory cells dropped over time, and the immune systems returned to normal in about two weeks. By that time 80% of the mice had accepted the grafts of insulin producing cells as their own. This acceptance rate is very high for transplantation, with mice normally rejecting grafts within 2-3 weeks. A graft is considered accepted if it's tolerated after 100 days. We took some mice out to 200-300 days, and not one of them rejected." [EurekAlert]

 

This is fantastic news for the transplant world. If immune-suppressing drugs can be removed from the procedure, those receiving transplants could lead healthier, and undoubtedly longer, lives.  Not to mention, cutting the drugs means cutting the cost of the procedure.  

 

But there is still a long way to go. The only surgery performed thus far dealt with the pancreas islet cells, which is relatively easy. The next step is to try more difficult procedures such as kidney transplants.  There is also the fact that these experiments have only been done in mice.  And while mice have long been one of the best models for human systems, there are of course differences in the way mouse and human immune systems work.  

 

However, Dr. Sprent is hopeful. "Those provisos given, if we were able to duplicate this experiment in humans, it would fulfill the dream of everyone in the transplant field." [EurekAlert]