The dominant antibody type present in the blood of transplant recipients may indicate their likelihood of experiencing organ rejection, according to a study which may help doctors identify patients who need aggressive treatments to safeguard the health of their new organ.

Transplant recipients who receive a kidney, heart, or lung often develop an immune response to the foreign tissue in the form of antibodies referred as donor-specific HLA antibodies. Some patients may already have these antibodies before their transplant because they have been exposed to blood products or previous transplants. Although the presence of donor-specific HLA antibodies in a recipient is usually not a good sign, not all patients who have them experience a poor outcome.

Through a collaboration of two transplant centers in France and the United States, Carmen Lefaucheur, MD, PhD (Saint-Louis Hospital, in Paris) and his colleagues designed a study to determine the greatest risk for losing a transplanted organ based on the characteristics and function of donor-specific HLA antibodies. Their study included 125 kidney transplant patients with donor-specific anti-HLA antibodies detected in the first year post-transplant.

The researchers found that the presence of certain donor-specific HLA antibodies--namely IgG3 and IgG4 subclasses--correlated with distinct patterns of antibody-mediated injury to the transplanted organ. Patients with mostly IgG3 donor-specific HLA antibodies had a higher likelihood of organ rejection soon after transplantation. If rejection occurred in those with mostly IgG4 antibodies, it was usually much later after transplantation.

"Our clinical investigation may help in the future to identify the patients that will require interventions to prevent the loss of a transplanted organ," said Dr. Lefaucher. "Also, based on what we learned in this investigation, more studies will be initiated to further elucidate why some patients seem to maintain good outcomes while others demonstrate accelerated deterioration of the transplanted kidney in the presence of circulating donor-specific HLA antibodies."

Published in the Journal of the American Society of Nephrology (JASN).