TEMPORAL AND QUANTITATIVE-ANALYSIS OF CHIMERISM IN LIVER AND KIDNEY-TRANSPLANT PATIENTS - AN ENHANCED FLUORESCENCE DETECTION SYSTEM ALLOWS FOR MORE SENSITIVE QUANTITATIVE DETECTION

Background: Because spontaneous microchimerism has been reported in st able renal and hepatic allografts, the presence of donor-derived cells in recipient tissues was investigated in kidney and liver transplant recipients. Methods and Results: Human lymphocyte antigen class II mar kers and Y-chromosome sequences in male donor-to-female recipient tran splants were used for chimeric analysis. Human lymphocyte antigen typi ng was performed by group-specific polymerase chain reaction amplifica tion and restriction fragment length polymorphism analysis, X-chromoso me-and Y-chromosome-specific primers were used in a multiplex polymera se chain reaction analysis. Quantitative Y-chromosome analysis was per formed using energy-transfer fluorescence from a nested primer system. Patients who had rejected their grafts were also analyzed, as were a group who were analyzed for chimerism at the time of transplant (day 1 ) and sequentially at various intervals for up to 3 months, Of 23 long -term kidney patients analyzed, 16 were chimeric by human lymphocyte a ntigen or sex-determination analysis. In 2 patients whose graft had fa iled no chimerism was observed. Chimerism in liver patients was detect able on the day of transplant and was maintained for 30 to 120 days as measured at 5-day intervals (these patients continue to be monitored) . Quantitative analysis suggested that the ratio of donor to recipient cells was variable in a patient and ranged from greater than 1 in 10( 4) to less than 1 in 10(5). An enhanced fluorescence energy-transfer d etection system was adopted to increase sensitivity of the polymerase chain reaction detection of chimerism and to quantitate the results. C onclusions: The results indicate that cells from the donor organ migra te into recipient tissues early after transplantation. These cells per sist in a majority of patients for at least 3 to 4 years. It has been proposed that tolerance is related to the presence of these ''passenge r'' leukocytes and that dendritic cells play the most important role. The data suggest that the establishment of chimerism plays an importan t role in graft acceptance in a majority of the kidney and liver patie nts in this study. These findings also suggest that the levels of chim eric cells, ''a quantitative chimerism,'' may be important in establis hing tolerance but further studies are required to support this conten tion.