In particular, two rare syndromes illustrate the importance of T cells in maintaining self-tolerance: the first, autoimmune polyglandular syndrome type I (APS 1, also called APECED), is caused by defects in the autoimmune regulator (AIRE) gene that mediates the induction of T-cell self-tolerance in the thymus30. The gene discussed is AIRE; the disease is autoimmune polyendocrine syndrome type 1.