Lessons on immune tolerance from the monogenic disease APS1.

Autoimmunity is a complex disease process that results from a breakdown in the ability of the immune system to discriminate self from non-self. One approach to unraveling how autoimmunity occurs is to study monogenic diseases, for which a single gene defect is responsible. Recent work on the monogenic autoimmune disease 'autoimmune polyglandular syndrome type 1' (APS1) and on the causal gene of this disorder--autoimmune regulator (AIRE)--is providing new lessons on how immune tolerance is maintained.