Five years after lung transplantation, fewer than half of the transplanted lungs are still functioning, according to the U.S. Organ Procurement and Transplantation Network. This compares with five-year organ survival rates of about 70 percent for heart, kidney and liver transplants.
The poorer outcomes after lung transplantation are related largely to higher rejection rates, the researchers said. About 1,800 lung transplants are performed each year in the United States.
"The high failure rate of lung transplants is a major problem," said co-corresponding author Alexander Krupnick, MD, a Washington University lung transplant surgeon at Barnes-Jewish Hospital. "Lungs are unique. Unlike other organs, they are continually exposed to bacteria, viruses and everything else in the environment, and we think this increases the risk of chronic rejection and the eventual failure of the organ."
Memory T cells regularly patrol the lungs, where they distinguish harmless challenges like cat dander or tree pollen from more serious insults like respiratory viruses or pathogenic bacteria. Without these cells, the immune system recognizes a newly transplanted lung as harmful and mounts an attack that eventually can lead to rejection of the organ.
As part of the study, the researchers performed lung transplants in mice. When memory T cells were absent in these mice, the newly transplanted lungs underwent rejection. The researchers found evidence of severe inflammation in the lungs, an indicator that the immune system had instigated an aggressive attack against the foreign organ.
However, when the scientists infused memory T cells into the lung recipients, they could reduce inflammation and prevent rejection. Further, they defined the molecular pathway by which memory T cells naturally dampen the body's response to lung transplants. Rather than attacking the lungs, memory T cells unleash
|Contact: Caroline Arbanas|
Washington University School of Medicine