An ABO incompatible kidney transplant is a procedure where a kidney is transplanted from a donor to a recipient who have different ABO blood types. Traditionally, such a mismatch would lead to immediate rejection of the organ by the recipient’s immune system. Advances in medical science now allow these transplants to occur successfully, significantly expanding the pool of available kidneys. This approach offers a viable option for many patients who might otherwise face prolonged waiting times for a compatible organ.
The Science of Blood Type Compatibility
The ABO blood group system classifies blood into four main types: A, B, AB, and O. This classification depends on the presence or absence of specific carbohydrate markers, called antigens, on the surface of red blood cells. For example, individuals with Type A blood have A antigens, while those with Type B blood have B antigens. Individuals with Type AB blood have both A and B antigens, and those with Type O blood have neither.
The body’s immune system naturally produces antibodies in the plasma that react against ABO antigens not present on its own red blood cells. When a kidney from an incompatible blood type donor is transplanted, these pre-existing antibodies in the recipient’s blood immediately recognize the foreign ABO antigens on the donor organ’s cells. This recognition triggers a severe immune response, known as hyperacute rejection, which can lead to rapid destruction of the transplanted kidney.
Making the Incompatible Possible: Medical Strategies
Overcoming ABO incompatibility requires specific medical interventions to neutralize the recipient’s pre-existing antibodies. This process, known as desensitization, involves several techniques to prepare the recipient’s immune system for the new kidney. One primary method is plasmapheresis, also called plasma exchange, which physically removes anti-ABO antibodies from the recipient’s blood plasma. During this procedure, blood is drawn, the plasma containing harmful antibodies is separated and removed, and remaining blood cells are returned with a replacement fluid or compatible plasma.
Another technique used is immunoadsorption, which selectively removes specific antibodies from the blood. This method targets anti-ABO antibodies more precisely than conventional plasmapheresis, reducing the removal of other beneficial plasma components. After antibody removal sessions, intravenous immunoglobulin (IVIG) is administered. IVIG, a solution of antibodies from healthy donors, helps modulate the recipient’s immune system, protect against infections, and neutralize remaining anti-ABO antibodies.
Powerful immunosuppressive medications are also a part of the desensitization protocol. Rituximab, a medication that targets B cells—the immune cells responsible for producing antibodies—is given before the transplant. By depleting these B cells, rituximab helps prevent the recipient’s body from generating new anti-ABO antibodies after the transplant. Other immunosuppressants like tacrolimus, mycophenolate mofetil, and prednisolone are also started before the transplant and continued long-term to suppress the overall immune response and prevent rejection of the new kidney.
Navigating an ABO Incompatible Transplant: What Patients Need to Know
Patients may consider an ABO incompatible kidney transplant when a living donor with a compatible blood type is not available, or to significantly reduce their waiting time for a deceased donor organ. This option allows family members or friends with different blood types to donate, expanding the possibilities for transplantation. The process begins with a thorough evaluation to determine suitability, including assessment of antibody levels.
Pre-transplant desensitization treatments span several days to weeks before the surgery. Patients undergo multiple sessions of plasmapheresis or immunoadsorption, which may involve regular visits to a clinic or hospital. During these sessions, patients might experience fatigue or minor discomfort, but the procedures are well-tolerated. Medications like rituximab and other immunosuppressants are also initiated during this pre-transplant period, requiring close monitoring for any side effects.
The transplant surgery is similar to a compatible kidney transplant, involving the surgical placement of the donor kidney. Following surgery, rigorous post-transplant care is necessary, which includes continued immunosuppressive medication to prevent rejection and regular monitoring of kidney function and antibody levels. Patients must adhere strictly to their medication schedule, as missing doses can increase the risk of rejection.
While modern protocols have improved outcomes, ABO incompatible transplants do have some unique considerations. Patients may face a higher intensity of initial immunosuppression, which can lead to an increased susceptibility to infections, such as those caused by the BK virus. There is also a higher risk of bleeding complications in the immediate post-transplant period, linked to the antibody removal procedures. Despite these considerations, long-term patient and graft survival rates for ABO incompatible kidney transplants are similar to those of ABO compatible transplants, ranging from 88% to 98% at one year and remaining favorable over several years. This makes ABO incompatible transplantation a safe and effective treatment for kidney failure.