Scientists Spot Key to Kidney Transplant Success

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The trouble is, MICA antigens can't be detected with the methods normally used.

"Normal tests cannot see this antibody, so, we started to investigate this antibody, [to see] whether it was involved in kidney transplant rejection," Zou said.

Zou's group had previously identified MICA antibodies in transplant recipients, so they developed a test to screen for the antibody.

For this study, Zou and his colleagues tested blood samples from 1,910 recipients of kidney transplants from deceased donors, looking for anti-MICA antibodies. The blood samples came from the University of Heidelberg in Germany, which keeps a large database on transplant donors and recipients.

Antibodies against MICA were detected in 11.4 percent of the patients. The presence of these antibodies was also associated with rejection of the new kidney.

The rate of transplanted organ survival over a year for recipients with anti-MICA antibodies was 88.3 percent, versus 93 percent for those without the antibodies.

Among first-time recipients of a kidney, the organ survival rate was even lower among those with antibodies (87.8 percent) than those without antibodies (93.5 percent).

And among those with good HLA matching, having anti-MICA antibodies was associated with poorer organ survival (83.2 percent versus 95.1 percent among those without the antibodies).

"There was a very strong positive association with the MICA antibody and rejection," Zou said. "That was a surprise for us."

It's not clear yet that the anti-MICA antibody causes the organ rejection, but these findings strongly suggest that this is the case.

According to an accompanying editorial, "HLA remains the cornerstone of transplantation immunology." However, detection of MICA antigens and their corresponding antibodies may represent "a new tool set for understanding the rejection of kidney transplants," the editorial authors wrote.

"I think this is definitely a potentially useful tool in monitoring patients for increased risk of rejection," said Dr. Mohanram Narayanan, assistant professor of internal medicine with the Texas A&M Health Science Center College of Medicine and chief of the Section of Clinical Transplantation for Scott & White. After standard blood and HLA typing, "this would be a third thing to look at to make sure they're not at risk for rejection," he said.