Scientists Spot Key to Kidney Transplant Success

A tough-to-detect antibody explains why even 'matched' organs get rejected.

By Amanda Gardner
HealthDay Reporter
Wednesday, September 26, 2007; 12:00 AM

Copyright © 2007 ScoutNews, LLC. All rights reserved.

WEDNESDAY, Sept. 26 (HealthDay News) -- Researchers say a newly discovered immune factor is associated with kidney-transplant rejections and may explain why otherwise well-matched organs end up being rejected.

"Our paper showed that if a patient has this MICA antibody, that is very dangerous," said Dr. Yizhou Zou, study lead author and assistant professor of internal medicine at the University of Texas Southwestern Medical Center at Dallas.

"Current tests cannot see this antibody, so, this suggests that it may be very useful to add antibody screening to current screening tests," he noted.

The study is published in the Sept. 27 issue of the New England Journal of Medicine.

According to the U.S. National Institutes of Health, more than 9,000 kidney transplants are performed in the United States each year, making it second only to corneal transplants as the most common transplant operation.

More than 73,000 people are on the waiting list for a kidney, making successful transplantation critical.

However, for a kidney transplant to have even a hint of success, the donor and the recipient must be compatible. Donors and recipients can be incompatible in two ways: because of a blood type incompatibility or because of human leukocyte antigens (HLA) antigen sensitization.

HLAs, which are found on the surface of nearly every cell in the human body, help tell the difference between normal body tissue and foreign substances. Antigens vary from person to person, and HLA typing helps determine how many antigens a donor shares with a recipient. If individuals are not HLA matches, the recipient may produce antibodies to the antigen, thus spurring organ rejection.

But even donor-recipient pairs who are HLA matches can end in rejection. That has suggested that other -- as yet unknown -- antigens might be involved.

"The question was why is there a rejection, when the donor and recipient were an HLA match?" Zou said.

Major-histocompatibility-complex class I-related chain A (MICA) antigens can also stimulate antibody production and, the authors hypothesized, they might also contribute to organ rejection. The MICA antigen is found on endothelial cells, or the layer of cells lining the inside of blood vessels.