Predominant Hematopoietic Origin of Cell-free DNA in Plasma and Serum after Sex-mismatched Bone Marrow Transplantation

Despite current interest in the biology and diagnostic applications of cell-free DNA in plasma and serum, the cellular origin of this DNA is poorly understood. We used a sex-mismatched bone marrow transplantation model to study the relative contribution of hematopoietic and nonhematopoietic cells to circulating DNA. We studied 22 sex-mismatched bone marrow transplantation patients. Paired buffy coat and plasma samples were obtained from all 22 patients. Matching serum samples were also obtained from seven of them. Plasma DNA, serum DNA, and buffy coat were quantified by real-time PCR of the SRY and beta-globin gene DNA. To investigate the effects of blood drawing and other preanalytical variables on plasma DNA concentrations, blood samples were also collected from 14 individuals who had not received transplants. The effects of blood sampling by syringe and needle, centrifugation, and time delay in blood processing were studied. The median percentage of Y-chromosome DNA in the plasma in female patients receiving bone marrow from male donors (59.5%) differed significantly (P