AIRE and Autoimmunity: Several mechanisms have been proposed to explain the increased susceptibility to autoimmunity in DS, which may include: (1) partial central tolerance failure due to altered thymic expression of the autoimmune regulator (AIRE) gene, which is located on chromosome 21and involved in immune regulation [73,83]; (2) thymic atrophy and T and B lymphocyte reduction [74]; (3) increased pro-inflammatory cytokine levels and decreased anti-inflammatory cytokine levels due to alterations in the extracellular adenine nucleotide and nucleoside levels [139,140].