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| |  HLA-Specific B Cells May Explain Higher Rejection Rates in Black Kidney Transplant Recipients BETHESDA, Md -- August 29, 2008 -- A research team reports it may have an explanation for at least some of the higher organ rejection rates seen among black, as compared with white, kidney transplant recipients. In a study of 50 healthy adult men, 25 black and 25 white, significantly different amounts of certain immune system cells were found between the races. Human leukocyte antigen-specific, or HLA-specific, B cells, when sensitised, produce antibodies linked to transplanted kidney rejection, said lead researcher Andrea Zachary, MD, Johns Hopkins Medical Institutions, Bethesda, Maryland. It has been long known that HLA-reactive antibodies produced by B cells are one of the ways that transplanted organs are rejected. Dr. Zachary developed a novel method for counting HLA-specific B cells more accurately, leading to the hypothesis that B cell numbers make a difference in transplant retention and rejection. "Now that we have an accurate way to count these cells, we are able to confirm what we long suspected, that blacks might have a bigger army of HLA-specific B cells," said Dr. Zachary, who presented her findings at the Congress of the International Transplant Society in Sydney, Australia, on August 12. Dr. Zachary said that patients become sensitised when exposed to HLA in blood or tissue that is not their own. Sensitised HLA-specific B cells then produce antibodies that attack transplanted organs containing foreign HLA. Patients can become sensitised from a blood transfusion, transplantation, or pregnancy. "If the recipient is not sensitised, B cells represent only a patient's potential for making antibodies," says Dr. Zachary. "However, about a third of patients in need of a kidney are sensitised since they're often on their second or third transplantation and may have undergone transfusions." In the study, Dr. Zachary and colleagues gathered blood samples from 25 adult black males and 25 adult white males. They were all healthy and all nonsensitised. They also gathered blood samples from 10 sensitised adult black males and 25 sensitised adult white males. Results showed that the black nonsensitised males tested had an average of 17.2% more HLA-sensitive B cells compared with the white nonsensitised males tested. Among the sensitised group, black males had an average of 22.9% more HLA-sensitive B cells compared with white males. "Knowing that blacks have an increased number of HLA-specific B cells -- which increases their opportunity for antibody-mediated rejection -- we may be able to customise treatments for black recipients to account for these differences and lessen the likelihood that the organ will be rejected," said Dr. Zachary.
SOURCE: Johns Hopkins Medical Institutions
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