Role of Thymus in Adoptive Tolerance

Abstract

Summary Specific homograft tolerance was induced in neonatal C3H mice with CBA spleen cells. These mice were test-grafted with CBA skin. After bearing successful CBA skin grafts for 2 months or longer they served as donors for “tolerant” thymus and bone marrow transplants. Adult intact and thymectomized C3H mice were irradiated and injected with 10 million “tolerant” bone marrow cells. The thymectomized mice were, in addition, supplied with a subcutaneous “tolerant” thymus graft. The irradiated recipients of “tolerant” thymus and “tolerant” bone marrow accepted CBA skin, demonstrating adoptive tolerance. They also rejected C57B1/6 skin, demonstrating that “tolerant” thymus can reconstitute immune recovery of thymectomized, irradiated bone marrow treated mice. Nontolerant thymus grafts were unable to abolish the transfer of adoptive tolerance by “tolerant” bone marrow, both in intact and thymectomized irradiated recipients. “Tolerant” thymus was capable of imposing specific homograft tolerance on irradiated recipients of nontolerant bone marrow, especially if these recipients were thymectomized at the time of irradiation. These results support the evidence of others that thymus plays an important role in immunologic tolerance.