Face transplants are at the cutting edge of medical technology: Only around 35 patients worldwide have had their facial skin, bones, muscles, and blood vessels replaced by those of a deceased donor. But now Charla Nash, one of just a handful of facial transplant recipients in the United States, is taking it a step further. As a subject in studies funded by the U.S. military, she's being weaned off the drugs that keep her body from rejecting the face she received in 2011.

Nash, who was attacked by an employer's pet chimpanzee in 2009, was a prime candidate for the surgery. The attack left her without lips, eyes, eyelids, or a nose. By taking a donated face, reconnecting nerves and blood vessels, and stretching it over the recipient's skull, doctors were able to create a much more functional -- and less jarring -- new face. But because the experimental procedure isn't covered by insurance -- and costs about $350,000 -- Nash and her doctors relied on U.S. military funding.

The hope is that military veterans -- around 50 or 60 of whom have sustained injuries in recent wars that make them good candidates for the surgery -- can benefit from expertise doctors gain from working on patients like Nash. All in all, the military has provided grants to 14 medical centers around the country to allow them to provide these surgeries.

Now Nash is taking the next step.

Whenever an organ is transplanted from a donor into a new host, rejection is a big concern. The host's immune system will constantly try to reject and kill the foreign tissue now attached to its body. To prevent this, organ recipients have to take drugs to suppress their immune systems, making them more vulnerable to all sorts of diseases. Doctors have to balance the risk of infection with the risk of rejection.

Because Nash has had relatively few problems with rejection, she's the star of the military's new study. Her doctors will wean her off the immunosuppressant drugs keeping her face healthy and replace them with Interleukin-2, which is usually used to treat cancers. They believe the drug might promote the health of the face while destroying cells trying to attack it.

The ultimate goal is to find some one-stop solution for organ rejection. If doctors can figure out a way to transplant faces without tying patients to a lifetime of immunosuppressant drugs, they may one day be able to offer wounded veterans transplants for other "non-vital" parts damaged in service, such as ears and limbs.

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