Scientists Spot Key to Kidney Transpla...(t be involved. The question was why...),Health

"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.

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."
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