Mixed chimerism has been demonstrated in organ red blood cell typing, human lymphocyte antigen typtransplant recipients surviving over a long period. Howing, and detection of human lymphocyte antigen class ever, little is known about the fate and movements of I soluble antigens. 1,2 However, these conventional techdonor cells following liver transplantation. In this study, niques are of limited value due to their low sensitivity. using rat male-to-female liver transplantation, we as-Recently, DNA amplification by the polymerase chain sessed microchimerism by semiquantitative polymerase reaction (PCR) has made it possible to analyze specific chain reaction (PCR). A PCR specific for the Y-chromo-DNA sequences from small amounts of DNA temsome (sex-determining region Y [Sry]) allowed the displates. 3 PCR has now been clinically applied to the tinction of small amounts of male cells in a large excess evaluation of engraftment and mixed chimerism. 4,5-7 of female cells. Nonimmunosuppressed Lewis recipients Mixed chimerism in long-surviving liver transplant of Lewis liver grafts survived ΓΊ60 days, and donor cells were detected in peripheral blood up to day 60 in four of recipients was first demonstrated by Kashiwagi et al. 8 six recipients. All immunosuppressed Lewis recipients in 1969. Since then, systemic mixed chimerism has survived for 60 days, and the donor cells were detected been demonstrated circumstantially in liver transup to day 60. Semiquantitative PCR demonstrated that plants using conventional methods. 9,10 Recently, Starzl in immunosuppressed Lewis recipients surviving ΓΊ60 et al. 11-14 used a molecular biological technique and days with no acute rejection episode, the donor-to-recipdemonstrated the presence of donor cells in clinically ient cell ratio remained ΓΊ1:1,000. In nonimmunosupstable liver transplants. However, details of the fate pressed Lewis recipients of ACI liver allografts, donor and movements of donor cells following liver transcells in peripheral blood decreased rapidly by day 7. In plantation remain unknown. immunosuppressed Lewis recipients of ACI liver allografts, donor cells were detected for longer periods, in Animals. Female and male Lewis (RT11) and Male ACI the genotypes of the recipient and donor have included (RT1a) rats weighing 200 to 250 g were purchased from Charles River, Atugi, Japan. Experimental Design. All liver transplant recipients were Abbreviations: PCR, polymerase chain reaction.
female Lewis rats. Male Lewis and ACI rats served as synge-
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