After six decades of attempting to solve chronic organ rejection, researchers at Houston’s Methodist Hospital and Pittsburgh University have met the challenge.
According to an article in Medical Xpress, their theory is based on the immune system’s ability to recall foreign cells.
Immune suppressing drugs have greatly reduced organ failure during the first year after transplantation. However chronic rejection is still the main cause for transplant failure.
As a result, patients will eventually undergo a second organ transplant and again face the inherent risks that accompany them.
The Immune System’s Memory
Cells in the body’s immune system are able to recognize foreign organisms. The advantage of the immune system’s memory is that at a later date it will recognize foreign invaders earlier and act even more efficiently.
Vaccines use the same format for long term protection against viruses and bacteria. Yet even with the help of drugs that suppress the immune system, this unique feature is having a harmful effect by causing transplanted organs to be rejected since the immune cells recognize the transplanted organ as an invader.
The teams at Houston and Pittsburgh tackled this problem with encouraging results.
About the Study
Using a mouse model organ transplant that had been genetically modified, the researchers showed that immune cells trigger an immune response when re-exposed to foreign cells.
The researchers also discovered that monocytes and macrophages were also able to remember foreign tissue, a capability that hadn’t been recognized before.
Macrophages are large white blood cells that are charged with clearing the body of bacteria and viruses. Monocytes mature into macrophages.
How the Transplanted Tissues Survived
Through molecular and genetic analyses, the researchers found that the Ig-like receptor-A (PIR-A) had to be present in order for the memory feature in immune cells to function.
To eliminate the memory response, the researchers either blocked the PIR-A with a synthetically engineered protein or genetically removed it.
Dr. Fadi Lakkis, a Transplantation Biology specialist, commented that this discovery leads the way to develop drugs that will lessen the need for immunosuppressive drugs and their serious side effects.
The scientists see many other diseases that would benefit from their new understanding of the immune system, including autoimmune conditions and cancer.
