The immune system generally protects you noxious substances such as microorganisms, toxins and carcinogens.

These harmful substances have proteins called antigens on their surfaces. As soon as these antigens come in to the body, the immune system recognizes them as foreign and attacks them.

In the same way, an organ that is not compatible can cause a reaction to a blood transfusion or a rejection of the transplanted organ. To help prevent this reaction, doctors “typify” both the donor of the organ and the person who will be receiving it. The more similar that the antigens are between the donor and the transplantee, the less possibility there will be that the organ will be rejected.

Even though the typification of tissue will ensure that the organ or tissue is as similar as possible to the tissues of the patient needing the transplant, generally compatibility is not perfect. No person has the same identical antigens of tissue as any one else, except identical twins.

Doctors employ a variety of drugs to inhibit the immune system and to stop the body from attacking the recently transplanted organ when the compatibility of the organ in question is not too close. If inhibitor drugs are not used, the body can launch an immune response and attempt to destroy the foreign tissue.

However, there are a few exceptions. Transplants of cornea rarely are rejected because they don’t have a blood supply, and so antibodies cannot get to the cornea to cause the rejection. Also, transplants between identical twins never cause rejection.

There are three kinds of rejection:

  1. Hyperacute rejection occurs only a few minutes after the transplant if the antigens are completely incompatible. The tissue must be removed immediately so that the transplantee doesn’t die. This type of rejection is observed when a transplantee is given the wrong type of blood.
  2. Acute rejection can occur any time from the first week after the transplant to about three months afterward. Everyone has some degree of acute rejection.
  3. Chronic rejection occurs over many years. The constant immune response of the body against the new organ will slowly damage the tissues or the organs that have been transplanted.


  • The function of the organ begins to diminish
  • General feeling of unwellness
  • Pain or inflammation in the area of the organ (rarely occurs)
  • Fever (rarely)
  • Flu-like symptoms, including chills, muscle pain, nausea, cough, and respiratory difficulties.

Symptoms depend on the organ or tissue that has been transplanted. For example, patients who reject a kidney can have a symptom of decreased urine, and patients who reject a heart can present symptoms of heart failure.

Tests and Examinations

The doctor will examine the area above and around the transplanted organ, which the patient might find feels sensitive to the touch (especially in the case of a transplanted kidney).

Frequently, there will be signs that the organ is not functioning appropriately, for example:

  • Hyperglycemia (pancreatic transplant)
  • Decreased urine output (kidney transplant)
  • Respiratory difficulties or less stamina when exercising (heart transplant)
  • Yellowish skin and bleeding more easily (liver transplant)

A biopsy of the transplanted organ can confirm if there is a rejection. Frequently, a biopsy is done routinely to detect if a rejection is imminent, even before symptoms occur.

When rejection is suspected in a transplanted patient, one or more of the following tests and examinations may be performed, before doing a biopsy of the organ:

  • Computerized tomography of the abdomen
  • X-rays of the thorax
  • Heart echocardiogram
  • Kidney arteriography
  • Kidney ultrasound
  • Laboratory tests for kidney activity or hepatitis


The objective of treatment is to verify that the organ or tissues that have been transplanted are functioning appropriately and also to inhibit the immune response. Inhibiting the immune response can prevent transplant rejection.

There are many different drugs that can be used to inhibit immune response. The doses of this medicine depend on the state of the transplantee. Medicine doses can be very high when the tissue is first being rejected, and then can be continued at a reduced dosage to avoid the rejection beginning to occur again.


Some organs and tissues are transplanted with higher rates of success than others. If rejection is present, the immunosuppressant medicines can stop it. In that case, the patient will take those same medicines for the rest of his or her life.

However, immunosuppressant treatment is not always successful.

Possible complications

  • Certain cancers (in some people who take strong immunosuppressant drugs over a long period of time)
  • Infections (due to the inhibition of the immune system)
  • Loss of organ/tissue function in the transplanted organs or tissues
  • Side effects of the medicines, which can be serious

When to contact a medical professional

Consult with a doctor if the transplanted organ or tissue doesn’t seem to be functioning adequately or if other symptoms appear. Also, call the doctor if you develop side effects from the medicines you are taking.


The blood classification ABO and the typing of HLA (tissue antigen) before a transplant can help to guarantee a close compatibility. You generally will need to take medicines to inhibit the immune system for the rest of your life, to avoid the rejection of tissue.

To help prevent a rejection, patients should take medicines faithfully and regularly after a transplant, doctors should be vigilant and attentive.