Panel reactive antibodies (PRA) are created by the body to attack foreign tissue, and can be triggered by blood transfusions, transplants, and pregnancy. PRA levels are important to monitor in kidney transplant candidates, as high levels can make it difficult to find a matched donor and increase the risk of organ rejection. Immunoadsorption and plasmapheresis are two techniques that can reduce PRA levels.
The body naturally produces many different antibodies that help protect against the invasion of foreign antigens. Antibodies can also be created by the body to attack tissue, especially the tissue of another human being. In these cases, an antibody called a panel reactive antibody (PRA) is created when foreign tissue is introduced. Blood transfusions, transplants and pregnancy can trigger the production of PRA. These antibodies target human leukocyte antigens (HLA) found in human tissue.
A panel reactive antibody test is a blood test that specifically looks for PRAs. This test measures the levels of PRA in the blood. PRA levels are especially important to monitor in patients awaiting a kidney transplant. If these antibody levels are high, it can be difficult to match a recipient with a donor organ. Higher patient PRA levels increase the chances that the body will reject an organ from a donor with normal to low PRA levels.
While pregnancy, prior transplants, and blood transfusions are common causes of elevations in panel reactive antibody levels, these events do not always result in elevations in PRA. Studies have shown that patients receiving certain medications, such as erythropoietin, had a decrease in the amount of blood transfusions needed and decreased PRA levels. Also, previous transplants generally cause PRA levels to rise if the patient’s body is trying to reject the transplant.
Monitoring of PRA levels is important with kidney transplant candidates. High levels of PRA mean doctors have a harder time locating a matched donor, which can present a problem if an immediate transplant is needed. This means that patients with a higher PRA count may have to wait much longer for a matched donor kidney. Patients with elevated PRA levels are also more likely to experience organ rejection and must receive a more advanced regimen of anti-rejection drugs.
Panel reactive antibody levels are based on percentage measurements. The percentages of PRA in the blood play a role in determining the odds of finding a matched donor. If a patient has a higher PRA level, say at 60%, 60 out of 100 donors will not match.
There are two techniques that have been shown to be effective in reducing the number of PRAs. Immunoadsorption and plasmapheresis are both PRA removal techniques. These two methods deal with removing antibodies from the blood, but in two different ways.
Immunoadsorption involves circulating the patient’s blood through a special machine. This machine is specifically designed for binding PRAs. The PRA attaches to a column in the machine, which removes the antibodies from the blood. The cleaned blood is then recirculated into the patient’s body.
Plasmapheresis is similar to hemodialysis. The patient is hooked up to a machine called a centrifuge. The red and white blood cells and platelets are separated from the plasma by the machine. The separated plasma, which contains the panel’s reactive antibody concentration, is discarded. New, clean plasma is replaced and joined with platelets and blood cells. The centrifuge then adds the new mixed blood to the patient.
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