Immune System and Its Disorders in Children with Down Syndrome

Abstract

Down syndrome is caused by extra genetic material from chromosome 21 and occurs in all ethnic groups and in different species. There are many comorbidities associated with Down syndrome, including developmental delay, congenital heart disease, gastrointestinal anomalies, increased risk of hematologic malignancies and various autoimmune conditions. It is also the most common genetic syndrome associated with immune deficiencies in which both innate and adaptive responses are affected. Defects in immunologic parameters have been identified in Down Syndrome and have been proposed as the cause of the increased severity of infections in children with Down Syndrome. Most of these infections occur in the respiratory tract, suggesting anomalies in humoral immunity. However, differences in immune responses have been reported, including mild to moderately reduced T and B cell counts, lack of normal lymphocyte proliferation during infancy, smaller thymus size compared to age group, mild to moderately reduced percentages of naive T cells and correspondingly reduced Treg cell counts, suboptimal antibody responses to vaccination, reduced total and specific immunoglobulin A in saliva, and reduced neutrophil chemotaxis. In this article, defects in different components of the immune system in patients with Down syndrome and their clinical implications will be discussed.