New Insight Into Why Kidney Transplant Rejections Happen

While medical advances have made kidney transplantations steadily more successful since the first surgery was performed in 1950, patients are still experiencing an alarming rate of kidney transplant rejections. Estimates suggest that within 10 years of their surgery date, around half of all transplants will have been rejected by the host’s immune system.

According to recent statistics, within the first month, 97 percent of patients who received a kidney transplant have functioning organs. After one year post-surgery, that number declines to 93 percent. Within three years of transplantation surgery, 83 percent of organs are still functional.

While these figures are promising, there is still a significant subset of transplant patient who lose their organs due to complications. One of the most common reasons why organ transplants fail is organ rejection, which occurs when the body’s immune system recognizes the donated organ as foreign tissue, and attacks it just as the immune cells would attack a pathogenic invader.

Physicians have historically organized organ rejection into two separate groups: acute and chronic. Patients who experience acute rejection lose the organ within a year of surgery, while chronic rejection takes multiple years to progress.

Immunosuppressant drugs are used to treat patients showing symptoms of acute rejection, while chronic rejection is largely considered to be untreatable. Despite their previous designation as separate diseases, new research suggests that acute and chronic rejection are actually both part the same continuum.

The researchers – from the Scripps Research Institute (TSRI) in California – used gene expression profiling to simultaneously compare and contrast the activity of thousands of genes, between different patients. The team analyzed kidney biopsy samples taken from 234 patients, and found that 80 percent of genes that were active in patients with acute rejection were common to those with chronic rejection.

“It’s all the same disease – whether it’s one month post-transplant or five years post-transplant,” said Professor Daniel Salomon, director of the Laboratory for Functional Genomics at TSRI. “Immune-mediated rejection is a single entity at the molecular level.”

Clinicians often try to reduce immunosuppressant treatment in those with chronic rejection due to side effects of the drugs, however this only serves to worsen the condition as the immune system continues to attack the donor organ. The implication of the new research on kidney rejection, is that physicians will be able to prescribe those immunosuppressant drugs currently used to treat acute rejection, for patients with chronic rejection as well. According to Salomon, these results will be most likely be the same for other forms of tissue transplant rejection, including lung, heart and liver.