Immunology and Rejection
The human immune system is very complicated. It enables you to defend your body against invasion by foreign protein substances, whether in disease-causing microbes or transplanted organs from another human being who is not genetically identical.
The process of immunosuppression attempts to prevent this immune response from occurring. Unfortunately, there are no currently available methods to suppress your body's response
to a foreign organ without also impairing its response to infections.
Several medications are used to suppress the immune system from rejecting your transplanted organ(s). The current medication regimen used in the Stanford program consists of some or all of the following:
- azathioprine
- mycophenolate mofetil
- sirolimus
- tacrolimus
- cyclosporine
- prednisone
- rATG (rabbit antithymocyte globulin)
- daclizumab
You will be placed on an individualized regimen suited to your needs. You may be using different immunosuppressive combinations and dosages at various times. The ideal goal of an individual medication regimen is to suppress organ rejection while minimizing drug toxicity and the susceptibility to infection.
Rejection
Episodes of rejection of your transplanted organ(s) occur at random times following surgery, and are most frequent within the first few weeks or months after surgery.
Cardiac Rejection
There are no reliable laboratory data or changes on physical exam to detect cardiac rejection. The microscopic examination of tissue obtained by cardiac biopsy is the only reliable method currently available to diagnose the onset or resolution of rejection.
In adults and older children routine heart biopsies are performed approximately every week for the first four weeks after the operation and then with less frequency, depending on your course. After six months, most patients can have routine biopsies every three months. The need for surveillance biopsies on a routine basis is indefinite. For additional information, please see cardiac biopsies.
Rejection episodes are expected to occur at some time in almost all patients. There is nothing other than taking the prescribed medications that you can do to prevent them. Treatment for rejection is determined by severity and the time interval since transplantation.
The treatment may include the administration of increased dosages of oral prednisone with subsequent decreasing doses to just above baseline or three days of intravenous Solu-Medrol, or both. For persistent or severe rejection, the administration of rATG, a course of a mono-clonal antibody, or a series of total lymphoid irradiation (TLI) may be added to the therapy. A follow-up biopsy is always done to assess the adequacy of your therapy.
Pulmonary Rejection
In the heart-lung and lung transplant patient, surveillance transbronchial lung biopsies are performed to exclude lung rejection. Bronchoscopies may be performed every two weeks for the first two months, monthly up to six months post-operatively, and whenever changes in pulmonary function warrant it. Treatment of pulmonary rejection is similar to that noted for cardiac rejection.