 Down Syndrome DS is the most common chromosomal abnormality among live-born infants. Through full or partial trisomy of chromosome 21, DS is associated with cognitive impairment, congenital malformations particularly cardiovascular, and dysmorphic features. In addition, immunological abnormalities are much more prevalent in individuals with DS. For example, DS is associated with increased susceptibility to infection, as revealed in 2009 during the influenza pandemic where the likelihood of death was 300 times greater for DS patients than the general population. DS patients have increased frequencies of autoimmune disorders and leukemias, yet curiously, have a decreased risk for allergic diseases, particularly asthma. Perhaps the most telling statistic for immunologic abnormality in DS patients is that respiratory tract infections are the most important cause of mortality in DS at all ages.Our studies have identified AIRE as a master control gene that is aberrantly decreased in persons with DS, leading to autoimmunity and immunologic abnormalities. AIRE autoimmune regulator, although encoded on chromosome 21, is also significantly reduced in expression in DS, where it may contribute to autoimmune and immune dysregulation. The investigators will test the hypothesis that immune dysfunction and autoimmune disease preferentially occur in DS as a consequence of deficient expression of AIRE in peripheral blood cells. 