Presence of donor- and recipient-derived DNA in cell-free urine samples ofrenal transplantation recipients: Urinary DNA chimerism

Background: Previous studies have indicated that microchimerism is present in body tissues, peripheral blood, and plasma of recipients after organ tra nsplantation. We hypothesize that donor-derived DNA may also be present in cell-free urine of renal transplant recipients and that the concentrations of urine DNA may be correlated with graft rejection. Methods: Thirty-one female patients who had renal transplantation were enro lled in the study. In women with male organ donors, the SRY gene on the Y c hromosome was used as a marker for donor-derived DNA. Real-time quantitativ e PCR for the SRY and beta-globin genes was carried out on cell-free urinar y DNA from these patients. Serial urine samples from a female renal transpl ant recipient undergoing an acute rejection episode were also collected and analyzed with the beta-globin quantitative PCR system. Results: SRY sequences were detected in the urine of 14 of 17 female patien ts with male organ donors. None of the 14 patients with female organ donors had detectable SRY sequences in urinary DNA. The median fractional concent ration of donor-derived DNA was 8.7% (interquartile range, 1.9-26.4%). Duri ng the acute rejection episode, urinary concentrations of the beta-globin g ene were markedly increased, with the concentrations re-turning rapidly to normal following antirejection treatment. Conclusions: Our results demonstrate that urinary DNA chimerism is present following renal transplantation. The measurement of urinary DNA using quant itative PCR may be useful for the diagnosis and monitoring of graft rejecti on. (C) 1999 American Association for Clinical Chemistry.