'Huge step forward': Scientists discover immune reaction behind pig kidney rejection in transplant patients
Transplanting gene-edited pig kidneys into humans has been hailed as a pioneering procedure and a way to help ease the shortage of organs available for those on transplant waiting lists.
Scientists, however, have been struggling to understand why these animal organs have been rejected not long after surgery. Now, they may have an answer.
In the first of two studies published Thursday in the journal Nature, researchers at NYU Langone Health have discovered immune reactions that may explain why these organs get rejected.
The team looked at the transplantation of a genetically engineered pig kidney into a patient who was brain dead but had a beating heart and was on a ventilator in the ICU. The family had donated the patient's body to science.
For more than two months after the surgery, the NYU Langone team performed biopsies and collected samples of blood, tissue and bodily fluid from the patient in a way that's "impossible" to do in primates or living patients, according to Dr. Robert Montgomery, lead author of the study and director of the NYU Langone Transplant Institute.
"We could really get a very dense set of data points from doing biopsies, taking blood samples, body fluid samples and create an atlas of what that immune response looks like," he told ABC News. "And that's what's really unique about the study. I think that this is probably the most deeply studied human in history."
The team learned that pig organs were being rejected due to an immune system reaction from specific antibodies -- which recognize and attach themselves to foreign substances so they can be removed from the body -- and from T cells, which are white blood cells that help the body fight off germs and other unfamiliar invaders.
After rejection, the team used an FDA-approved drug combination to successfully reverse it, with no signs of permanent damage or reduced kidney function.
"It's a huge step forward," Montgomery said. "I think it makes transplantation just that much more of a successful endeavor. As we move forward, I do believe that we will be in a position in the next few years where gene-edited pig organs will be an alternative to human organs."
In a second study published in Nature, Montgomery and his team looked at the body's immune response to the pig organ in greater detail. By measuring levels of biomarkers in the blood, they were able to spot an attack up to five days before it would be visible in bodily tissue.
Montgomery said this can help transplant teams anticipate a potential rejection sooner and diagnose it quickly so it can be subsequently treated.
More than 101,000 Americans are in need of a kidney transplant but only 17,000 receive a transplant every year, according to the National Kidney Foundation.
Additionally, 12 people die every day while waiting for a kidney. The average wait time on the transplant list can be as long as 10 years. Montgomery said finding a way for more people waiting on the list to receive a kidney with gene-edited pig organs, while lowering the risk of rejection, is crucial.
"That's a great shortcoming of our health care system that we have to ration something that we know works so well," Montgomery said. "I think we really do need an alternative source of organs to really change this game."
The procedure, while considered by many to be a medical breakthrough, is still controversial, with some critics expressing ethical concerns about altering animal organs and potential health risks for patients.
Some patients who have undergone the procedure have had the genetically modified pig kidneys removed after organ rejection or unrelated infection. At least two patients have died after transplantation, although doctors say these patients were terminal and were experiencing end-stage kidney disease.
