The Autoimmune Regulator (AIRE) is a human transcription factor expressed at higher level in thymus, pancreas, adrenal cortex, and testis. It is expressed at lower level in the spleen, fetal liver and lymph nodes. It contains zinc finger motifs and isoform 1 is localized to both the nucleus and cytoplasm. Three splice variant mRNAs products have been described. In the thymus it causes transcription of a wide selection of organ-specific genes which create proteins that are usually only expressed in peripheral tissues, creating an "immunological self-shadow" in the thymus. Defects in AIRE are a cause of autoimmune poly-endocrinopathy candidiasis ectodermal dystrophy (APECED), also known as autoimmune polyglandular syndrome type I (APS-1).