We recently reported systemic autoimmunity following reconstitution of the lymphoid compartment of Rag1−/− mice with PD-1−/− hematopoietic stem cells or by transfer of thymocytes, but not splenocytes, suggesting that programmed death-1 (PD-1) plays a crucial role in controlling recent thymic emigrants (RTE) and preventing autoimmunity upon their LIP. The gene discussed is PDCD1; the disease is Autoimmunity.