Donor-type microchimerism is a phenomenon which occurs in some recipients after kidney transplantation (KT) and has been considered to play an important role to the induction or maintenance of allograft tolerance. In order to study the relevance of microchimerism to the long-term outcome of renal allograft, we retrospectively analyzed the presence of microchimerism in peripheral blood (PB) of 17 male-to-female kidney transplant recipients who had a stable graft function for 10 years or longer post-transplantation. Donor-type microchimerism, tested using nested\u2013PCR amplification for the SRY region of the Y-chromosome, was detected in 10 of 17 cases (58.8%) and in 7 of 17 cases (41.1%) with graft survival within 10 years and 15 years, respectively. Our results suggest that PB-DNA chimerism is present in a significant percentage of the long-term survival female kidney recipients from male donors, making useful the monitoring of chimeric status in these patients
