One of the critical problems doctors face when it comes to transplant surgery is convincing the body of the recipient to accept the new organ. Organ rejection is caused by the immune system of the recipient as it reacts to something in the body that did not originally grow there. Any foreign substance, whether a bacteria, virus, or transplanted organ, is seen by the immune system as a potential danger to the body. The natural response of the immune system is to attack the foreign object to destroy it before it can do damage.
What causes organ rejection?
The immune system uses cells called lymphocytes or white blood cells to locate cells that are recognized as not being part of the body, or “self”. Some white cells latch onto a cell that is “not self” to weaken and destroy it. When a donor organ is placed in the body, the white blood cells do not recognize the new tissue and attack it. Depending on the circumstances, this can happen soon after a transplant or it can happen weeks or months after the transplant is complete.
By studying human tissues, scientists have identified certain factors known as antigens that can cause a transplanted organ to be rejected. If the donor and the recipient have the same antigens, the white cells are less likely to notice that the organ is “not self” so the organ is less likely to be attacked. A more familiar example of this kind of matching is blood type. Doctors must be careful to match the type of blood, whether type O, A, B, or AB, before giving a blood transfusion because the wrong type of blood can make the recipient sick. In the same way, doctors must match the antigens between the donor and recipient to improve the odds that the organ will not be rejected.
Matching antigens to find a donor
Similar to blood transfusions, doctors must match the antigens between an organ donor and the recipient to improve the odds that the organ will not be rejected. As the number of matching antigens goes down, the odds of the organ being rejected goes up. Because there are many antigen combinations, it is difficult to find a perfect match aside from identical twins. Antigens development is controlled by genetics. This means people who are closely related are more likely to have matching antigens than people who are not related. Racial and ethnic backgrounds also influence individual antigens. So if a close relative is not available to be a donor, doctors will next look for a donor who has the same racial or ethnic background.
Drugs to prevent rejection
Many organ transplants are done with organs that are not perfect matches between the donor and recipient. In order to reduce the chances that the organ will be rejected, scientists have developed drugs known as immunosuppressants. As the name suggests, these drugs suppress the immune system to keep white cells from noticing the “not self” tissue that has been surgically added to the body. Unfortunately, someone taking immunosuppressants will also be more likely to develop other infections because the immune system is not able to function at full strength because of the drugs. Some people are gradually able to stop taking drugs for immunosuppression after transplant surgery. But most recipients will need to take the medications for the rest of their lives.
Even with the use of immunosuppression drugs, the recipient’s body may try to reject the organ. Doctors carefully monitor all transplant patients to watch for symptoms that the organ is under attack by the immune system so they can make appropriate adjustments to the medications to stop the rejection process.
Organ donors give hope
Organ donation is often considered a “last resort” when there is no other option for the recipient. Over 100,000 people in the United States are crucially ill and waiting for an organ to become available for their transplant surgery. Their only hope is that someone with matching antigens will chose to be an organ donor. Having more donated organs available improves the odds that a match will be available for each person on the waiting list. To find out more about how you can include organ donation in your advance directives, visit the Donate Life America website.
Sources:
Encyclopedia Britannica
Organ Procurement and Tranplantation Network
University of Maryland Medical Center
National Institutes of Health: Medline Plus
Transplant Living