| 1. Introduction Immunosuppressive agents decrease the rejection episodes in the early stage after transplantation, however there are some problems, such as how can we synchronously protect both allograft with better function and host with comparatively normal immune system. To further more resolve the rejection and such problems, donor specific tolerance were put forward as a better strategy. Notwithstanding the objections, chimerism were regarded as an especial role in the inducement of donor specific tolerance by most specialists and scholars. Chimerism means the symbiotic state of donor and host derived cells in recipient after transplantation. If the percentage of donor cells beyond 1%, it is called chimerism, and less than 1%, called microchimerism(MC). On the other hand, donor specific bone marrow (DSBM) transfusion were regarded as an effective approach to induce donor specific tolerance by enhance chimerism probably. In the April of 1999, the renal disease center (in the NO.1 hospital of Zhejiang University Medical School) launched out into a clinical trail about DSBM transfusion. To the November of 2000, 40 6 cadaver renal allograft recipients have received DSBM transfusion. The objective of this study is to establish two methods (nested PCR-SSP and PCR-SRY) to detect chimerism, and try to affirm the effect of DSBM transfusion to chimerism and compare the different modes of DSBM transfusion. 2. Methods According to the accepting and eliminating standards, 59 recipients were screened out, 23 of them accepted DSBM transfusion after cadaver renal transplantation (BM group). 20 of them belong to the control group who accept the other kidney of same donor, and 16 of them belong to the long term survived group who live with the good functional allograft more than 4 years. The lymphocytes were harvested from fresh anti-coagulated peripheral blood obtained on schedule (1 week, I month, 2-3 months, over 6 months after transplaniation for BM and control group, over 4 years after transplantation for long term survived group). Then through the extract of genomic DNA, affirmance of the donor and recipients HLA-DR alleles, nested PCR-SSP or PCR-SRY and electrophoresis to detect trace donor specific gene fragment and further to detect the chimerism or microchimerism. 3. Results 3.1. Comparing the BM group ~with control group, there is no obviously difference about cases constitution such as gender (P=0.331), side of allograft (P=0.280) and age (P=0.918). The comparison between the subgroups (twice and thrice) of BM group is same. 3.2. The acuity of the methods has been tested by artificial chimerism. The PCR-SRY can detect the male chimeric cells over 1% in the peripheral lymphocytes of female recipients and the 7 nested PCR-SSP can detect the microchimerism over 0.0 1% in any case in spite of the gender. The specificity of the methods has been tested by series control experiments. In the using of nested PCR-SSP, 2 recipients (one in BM group and another in control group) demonstrated as false positive. 3.3. Use nested PCR-SSP to detect chimerism...
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