Altered peripheral blood leukocyte subpopulations, function, and gene expression in children with Down Syndrome: Implications for respiratory tract infection.

OBJECTIVES: We tested the hypothesis that aberrant expression of Hsa21-encoded interferon genes in peripheral blood immune cells would correlate to immune cell dysfunction in children with Down syndrome (DS).

STUDY DESIGN: We performed flow cytometry to quantify peripheral blood leukocyte subtypes and measured their ability to migrate and phagocytose. In matched samples, we measured gene expression levels for constituents of interferon signaling pathways. We screened 49 children, of which 29 were individuals with DS.

RESULTS: We show that the percentages of two peripheral blood myeloid cell subtypes (alternatively-activated macrophages and low-density granulocytes) in children with DS differed significantly from typical children, children with DS circulate a very different pattern of cytokines vs. typical individuals, and higher expression levels of type III interferon receptor Interleukin-10Rb in individuals with DS correlated with reduced migratory and phagocytic capacity of macrophages.

CONCLUSIONS: Increased susceptibility to severe and chronic infection in children with DS may result from inappropriate numbers and subtypes of immune cells that are phenotypically and functionally altered due to trisomy 21 associated interferonopathy.