1578 Lyt - I CELLS CAN PREVENT AUTOIMMUNE DISEASE

Various organ-specific autoimmune diseases can be readily induced in some strains of mice by thymectomy during the critical neonatal period (NTx), 1 on day 2-4 after birth, without any exogenous sensitization with autoantigen (I-4). ~t is assumed in this model that NTx may eliminate T cells that would otherwis6 ontogenically peripherize via the thymus after the day of thymectomy (Tx), and may consequently allow the residual population of T cells that have already peripherized before Tx to respond to self-antigen(s) and eventually to cause autoimmune diseases in adulthood. In other words, NTx may deplete a subpopulation of T cells that in the normal state should suppress or regulate self-reactive clones. If this assumption is correct, then it should be possible to prevent the development of autoimmune disease by reconstituting NTx mice with the appropriate lymphoid cells. In fact, it was demonstrated that autoimmune diseases induced by NTx could be prevented by inoculation of splenic T ceils or thymocytes from normal syngeneic adult mice (4-6). In this study we have attempted to characterize the regulatory T cell population that is capable of preventing autoimmune oophoritis by cell surface antigens, particularly Lyt antigens, and other immunobiological features. The cells responsible for preventing the development of oophoritis in the spleens were found to be Thy-1 +, Lyt-l+,23 cells, and were not eliminated by adult thymectomy (ATx). Thymocytes having such a preventive capacity were also found to be Lyt-l+,23 -. Thus, the depletion of this Lyt-1 regulatory subpopulation by NTx may result in the development of oophoritis as well as other post-thymectomy autoimmune diseases.