Serologic Demonstration of a Thymus-Dependent Population of Lymph-Node Cells¹ Free

The aim of the present study was to determine whether the sensitivity of murine lymph-node cells to isoantibodies against the ϑ and Ly-antigens depends on the presence of the thymus. Neonatal and adult mice of various strains were thymectomized and their lymph-node cells tested at various intervals after thymectomy. Following either neonatal or adult thymectomy, the lymph-node cells of RIII/Jem mice lost their sensitivity to the cytotoxic effect of ϑ-AKR antibodies. The lymph-node cells of neonatally thymectomized C57BL/6 mice became refractory to the cytotoxic effect of ϑ-C₃H antibodies, whereas the cells of neonatally thymectomized DBA/1 mice became refractory to ϑ-C₃H and Ly-antibodies. In C₃H/An mice, neonatal thymectomy resulted in an almost complete loss of the sensitivity of lymph-node cells to ϑ-C₃H and Ly-antibodies. Some neonatally thymectomized RIII mice were grafted with allogeneic thymuses, and their lymph nodes were examined 2 to 3 weeks later. The lymph nodes of such reconstituted animals contained cells displaying the ϑ isoantigenicity distinctive for the thymic graft. In addition, these lymph nodes contained a slightly greater number of host cells sensitive to ϑ antibodies than did the lymph nodes of thymectomized littermates which did not receive thymus grafts.

These results indicate that the lymph-node cells which are sensitive to the cytotoxic effect of ϑ and Ly-isoantibodies are thymus-dependent, and that at least some of them are thymus-derived. Moreover, the thymus may possibly affect the expression of the ϑ and Ly-antigens in lymph-node cells by an indirect control mechanism.