AIRE and autoimmune disease: The observed deficiencies in mTEC, AIRE expression and thymic T regulatory cells are thought to underlie the propensity for autoimmune disease and OS, particularly in patients with “leaky” SCID, in which very limited residual intrathymic T cell development does occur but in the absence of a thymic microenvironment suitably developed for central tolerance induction [22, 136, 137].