The advancement, called positive crossmatch transplants, greatly reduces the chance of organ rejection in patients with elevated antibody levels. Previously, these elevated antibody levels made tissue rejection almost certain.

Mayo Clinic is one of three medical centers in the United States that offer this procedure.

About 45,000 people are waiting for a cadaver kidney in the United States; about 8,000 kidneys are available every year.

About 7,000 of those waiting are affected by this elevated antibody level. "The only option available for these people was to stay on dialysis," says Mark Stegall, M.D., a Mayo Clinic kidney and pancreas transplantation surgeon. "It was very unlikely they would ever get a transplant."

Dialysis works like an artificial kidney. It prolongs life but it is not ideal. Three times a week for four hours at a stretch, patients hook up to a machine that removes waste fluids and regulates the body’s chemical and blood balances.

Physicians aren’t certain what causes patients to have elevated antibody levels that make traditional transplants likely to fail. Many of those with elevated antibody levels have had a previous failed kidney transplant. Others have had multiple pregnancies or multiple blood transfusions. Many are young or middle-aged adults who are otherwise healthy.

Improved results by removing antibodies

Prior to a positive crossmatch transplant, patients undergo a dialysis-like process called plasmapheresis, where the antibodies that cause tissue rejection are removed. The risk of rejection is also reduced by new medicines that specifically target cells that make the antibodies and removing the patient’s spleen which is responsible for antibody production.

The positive crossmatch process is similar to the process used for ABO-incompatible living-donor kidney transplants -- another recent advancement in transplants -- where patients can receive kidneys from living donors with blood types different from their own.

"With positive crossmatch transplants, we are taking it a step further, making it possible for the patients to accept different tissue types in addition to different blood types," says Dr. Stegall.

So far, Mayo Clinic surgeons have performed 20 ABO-incompatible kidney transplants and four positive crossmatch kidney transplants.

"The results and recovery time for both positive crossmatch and ABO-incompatible transplants are similar to other living-donor kidney transplants," says Dr. Stegall. "That’s remarkable, especially for the positive crossmatch patients. Before this, they didn’t have the option of a transplant."

Living donors are used for both ABO-incompatible and positive crossmatch transplants. About 150 of the 200 kidney transplants performed this year at Mayo Clinic will use living donors.

Using living donors offers many benefits: a shorter waiting time for transplants; kidneys can be tested prior to transplant; they routinely function immediately while cadaver kidneys may take several weeks to work; and they typically last much longer than kidneys from cadavers.

Positive crossmatch kidney transplants move medical science one step closer to xenotransplantation (pig-to-human organ transplants). "The barrier to putting a pig kidney into a human is the presence of antibodies," says Dr. Stegall. "With positive crossmatch transplants, we have crossed that antibody barrier in a human-to-human transplant."

"We hope to take what we’ve learned here to move closer to xenotransplantation, a transplant option that we hope will alleviate years of waiting for donor organs," says Dr. Stegall.

Note: If no author is given, the source is cited instead.

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