The job of the immune system is to prevent infection and illness by attacking foreign matter in the body. This is a useful task, and a necessary one except when the supposedly foreign matter shouldn’t be attacked. One example of this is auto-immune disease, in which a healthy, innocuous organ—the bowels, the skin, the lungs, the thyroid gland, the pancreas, or any organ—is misidentified by the immune system as an infectious agent and duly attacked. Another example is organ transplants. A transplanted organ actually is foreign matter, but it is not a threat. This is why it is important that the donated organ be as close a match as possible for the recipient’s body—to minimize the immune response. Even with this precaution, however, it is often necessary for transplant recipients to take medication that inhibits the immune system for the remainder of their lives.
Transplant rejection can be observed as soon as minutes after the transplant, or months or even years later. It manifests as an often life-threatening inflammatory response, and the transplanted organ fails. The inflammation, however, can affect other parts of the body as well, making it important for doctors to avoid it. Transplant patients are also at risk for chronic transplant rejection, in which the immune response happens slowly over a long period of time. This is particularly common with lung transplants. Chronic rejection causes transplanted organs to be more than usually prone to injury and inflammation, and to function less well than would ordinarily be inspected.
Because immune-suppressing medications leave the patient vulnerable to opportunistic infections, medical researchers are looking into other ways to prevent rejection. One line of investigation is using the patient’s own stem cells—cells found in bone marrow that carry the patient’s genetic material, and are therefore recognized by the body, but that are not associated with any specific organ—to construct custom transplant organs. This process is in its infancy, but if perfected, would ease reliance on donors.
Another approach is to simply restart the immune system, convincing it the transplanted organ was there all along. When successful—and it has been successful in trials in kidney transplant recipients—immune rebooting replaces immune cells that recognize the organ as foreign with new ones that accept it from the start. This means patients can replace a cocktail of toxic immune suppressants with a mere handful, with a reduction in side effects.