Why does organ rejection occur?

Your body has a natural defense system called the immune system that protects you from infection and disease. The immune system defends your body by producing antibodies and "killer" cells that destroy foreign substances (such as viruses and bacteria). Since the donor organ doesn't match your own tissue exactly, your body tries to destroy the transplanted organ by rejecting it. Rejection is nature's way of protecting your body.

What medicines will I need to take?

After an organ transplant, you will need to take antirejection medicines, or immunosuppressants, for as long as you have the donor organ. Because your immune system will try to destroy the new organ, antirejection medicines are needed to decrease your immune system's response so the new organ stays healthy.

Antirejection medicines weaken your immune system and decrease your body's ability to fight infections, cancer, and other diseases. Over the years since organ transplants were first done, these medicines have greatly improved. Researchers are finding out more all the time about how to better regulate the immune system after a transplant. Current medicines still have the potential to speed up illness or create new disease, such as heart problems, diabetes, cancer, and osteoporosis. But these medicines also will save your life by keeping your body from rejecting the donor organ. It is important to take these medicines daily and exactly as prescribed.

Taking medicines daily for the rest of your life is not as hard as it sounds. It may help to talk to someone who has had a transplant and who can give you some assurance that you will be able to make the medicines a part of your daily routine. Over time, probably, fewer medicines will be needed. Additional medicines may occasionally be needed to fight infection or other health problems related to your transplant.

Generally, the antirejection medicines you will take after an organ transplant include:

Corticosteroids, such as prednisone or methylprednisolone. A high dose of corticosteroid, often methylprednisolone, is given right before your transplant, to decrease your immune system's activity, reduce inflammation, and prevent rejection. High doses of corticosteroids are usually continued for a few days after your surgery and then tapered to the lowest dose that helps prevent rejection. Taking high doses of corticosteroids for just a few days may cause temporary side effects such as high blood pressure, high cholesterol, weight gain, sleep problems, and anxiety. High doses can sometimes cause more severe side effects, such as extreme agitation, paranoia, and psychosis (trouble telling the difference between what is real and what is not real)-some people may feel "out of it" or have hallucinations while taking high doses of steroids. But these side effects are temporary. Prolonged use of corticosteroids can cause glaucoma, steroid-induced diabetes, and increase your risk of getting an opportunistic infection (such as pneumocystis pneumonia), which is a type of infection that occurs in people with weakened immune systems. Some experts are finding that some people may be able to avoid use of steroids or to use them sparingly.