The immune system is the body's defense mechanism. It is very complex but vital to maintaining overall health. It attacks any "foreign" substance that enters the body, including infectious organisms such as bacteria and viruses. By a series of steps, it finds the foreign material and attacks it.
There are two major genetic systems in the body that affect the immune system's response to a transplant, ABO and HLA. Generally speaking, a close genetic match between the kidney donor and the kidney recipient reduces the risk of rejection.
ABO (Blood Type)
All humans have one of four blood types, A, B, O, or AB. The first test of a "match" is to determine ABO compatibility. You do not necessarily have to have the exact same blood type to be compatible. There are so called "universal recipients" (AB) and "universal donors" (O) for blood.
HLA (Human Leukocyte Antigen)
This system is much more complex than the ABO system and involves the matching of antigens in the blood and tissues of the donor and candidate. Antigens recognize something as "foreign" to the body and produce antibodies, which then attack the foreign object. This process is called the immune response. This procedure is called "tissue typing."
Both systems involve inherited traits, which is why parents, siblings, and offspring can make the best possible match. However, because we receive different genes from both parents, no relatives except identical twins (who have the same genes) will ever be a "perfect" match. There are infinite degrees of compatibility which influence the short and long term risks of rejection. The idea behind successful transplantation is to get the best possible match to reduce the chances of the immune response activating and attacking the donated kidney.
With transplantation, the new organ will be recognized as foreign by the immune system, and will react against it. This process is called rejection. In order to prevent and limit the immune system's rejection to the new kidney, patients will take medications to suppress or reduce the normal immune responses. These drugs are called immunosuppressants. While immunosuppressants limit organ rejection, they also lower the body's defense against infectious organisms, thereby increasing susceptibility to infections.
Current immunosuppressant drugs are: Cellcept, Neoral or Prograf, Prednisone, Rapamune, Solumedrol, Campath, Zenapax, Thymoglobulin and OKT3. In our transplant center we use an approach of in Induction and Maintenance therapy. Induction covers the medications given at the time of transplant surgery, while Maintenance includes the medications taken after the transplant for as long as the kidney is working. Each transplant recipient will be placed on a regimen best suited to that individual. Different combinations and dosages of the medications may be used at different times, but the goal is to prevent kidney rejection while minimizing the side effects to the patient. A significant amount of research is done to find immunosuppressive agents that prevent kidney rejection and produce fewer side effects.