ANALYSIS OF PCR MICROCHIMERISM INDUCED BY INTRATHYMIC INOCULATION OF DONOR ALLOANTIGENS IN RATS

Intrathymic injection of donor alloantigens (splenocytes) was performe d in rat heart transplantation to induce tolerance. In our experimenta l protocol, male (BN rats, RT1(n)) heart allografts were transplanted to female (LEW rats, RT1(l)) recipients in order to detect the existen ce of Y-chromosomes in recipients' tissues using the polymerase chain reaction (PCR) after the establishment of microchimerism. The mean sur vival time (MST) of male heart allografts was prolonged by the thymic injection protocol. PCR analysis of the Y-chromosomes of these recipie nts showed that splenocytes inoculated into the thymus still remained after as long as 30 days, while none of the cells that originated from the donor were never detected in the peripheral blood. On the other h and, our previous study demonstrated that the donor-specific Y-chromos omes could be detected in all the tissues of the females (peripheral b lood, lymph nodes, spleen, and liver) except for thymus, of the sex-mi smatched rat liver transplantation without thymic injection. Completel y inconsistent results n ere deduced from two of our experiments, but the present study demonstrated that thymic clonal deletion played a ma jor role in the prolongation of allograft survival after intrathymic i njection of donor alloantigens.