Kidney donation is a life-saving procedure for individuals with end-stage renal disease. While compatibility is important, medical advancements have expanded the possibilities for successful transplants beyond a perfect match. This article clarifies what matching entails and the various donation options.
Understanding Compatibility
“Matching” in kidney donation involves several biological factors that determine how well a donor’s kidney will be accepted by a recipient’s body. Blood type compatibility is the first step, following the same rules as blood transfusions. An O blood type donor is universal, able to give to any recipient (A, B, AB, or O). Conversely, an AB blood type recipient is universal, able to receive from any blood type.
The next crucial factor is Human Leukocyte Antigen (HLA) tissue typing. HLAs are proteins found on the surface of most cells, acting as markers that help the immune system distinguish between “self” and “non-self.” There are six primary HLA markers (A, B, and DR) considered most important in kidney transplantation, with three inherited from each parent. While a closer HLA match can lead to better outcomes, successful transplants frequently occur even with several mismatches due to modern immunosuppression.
Finally, a crossmatch test detects pre-existing antibodies in the recipient’s blood that could react against the donor’s cells. A positive crossmatch indicates the recipient has antibodies that would likely attack the donor’s kidney immediately, making the transplant too high-risk to proceed. Conversely, a negative crossmatch suggests compatibility and a lower risk of immediate rejection.
The Significance of Compatibility
Compatibility is important because the recipient’s immune system recognizes the transplanted kidney as foreign tissue. Without adequate matching, the immune system would attack, leading to organ rejection. This immune response can manifest as acute rejection, occurring shortly after the transplant, or chronic rejection, which develops over a longer period.
A better match can help reduce the intensity and dosage of immunosuppressant medications required after transplantation. These medications, while necessary to prevent rejection, can have various side effects and increase the recipient’s susceptibility to infections. A closer match can also contribute to better long-term survival of the transplanted kidney, also known as graft survival.
Navigating Non-Matching Scenarios
When a direct donor-recipient match is not possible, several strategies can still facilitate a life-saving kidney transplant. Paired kidney donation, also known as a kidney exchange program, is a common solution. In this program, two or more incompatible donor-recipient pairs “swap” kidneys. For example, if Donor A is incompatible with Recipient A but compatible with Recipient B, and Donor B is incompatible with Recipient B but compatible with Recipient A, a swap can occur, allowing both recipients to receive a compatible kidney. This system significantly broadens donation opportunities for incompatible pairs.
Another pathway is altruistic, or non-directed, donation. An altruistic donor is an individual who donates a kidney to someone they do not know, without a specific recipient in mind. These donations can initiate a “chain” within a paired exchange program, where the altruistic donor’s kidney goes to a recipient in one incompatible pair, allowing that recipient’s donor to then donate to another incompatible pair, and so on. This can lead to multiple transplants from a single altruistic act.
In certain specific cases of incompatibility, medical procedures like desensitization may be considered. This complex process aims to reduce harmful antibodies in the recipient’s bloodstream that would otherwise cause rejection. Techniques such as plasmapheresis are used to filter out these antibodies. While desensitization can enable transplantation for highly sensitized patients, it is a specialized and intensive treatment, not a universal solution for every non-matching situation.