title: Distinct abnormalities in the innate immune system of children with Down syndrome.
abstract: OBJECTIVE
  To analyze the frequency and phenotype of cells of the innate immune system in the peripheral blood of children with Down syndrome (DS).
  
  
  METHODS
  Flow cytometric analysis of expression of cell surface markers was performed in children with DS (n = 41) and healthy age-matched controls (n = 41).
  
  
  RESULTS
  Compared with controls, children with DS had significantly lower absolute total leukocyte counts, lymphocytes, monocytes, and granulocytes, but 1.5-times higher absolute numbers of CD14(dim)CD16(+) monocytes (147 x 10(6)/L vs 93 x 10(6)/L; P = .02). This difference is fully explained by a higher percentage of CD14(dim)CD16(+) monocytes within the monocyte compartment (28.7% vs 13.4%; P <.001). The absolute numbers of myeloid dendritic cells were lower in DS (13.8 x 10(6)/L vs 22.7 x 10(6)/L; P <.001). The numbers of plasmacytoid dendritic cells and natural killer cells were normal. Absolute numbers of invariant natural killer T cells were very low overall, but significantly lower in children with DS than in controls (1.2 x 10(6)/L vs 3.7 x 10(6)/L; P = .01).
  
  
  CONCLUSIONS
  Children with DS exhibited distinct abnormalities in cells of the innate immune system. Most strikingly, they had a high number of proinflammatory CD14(dim)CD16(+) monocytes. This elevated level of CD14(dim)CD16(+) monocytes may play an important role in the onset and maintenance of chronic inflammatory disease in DS.
authors.affiliation: Department of Pediatrics, Division of Infectious Diseases and Immunology, University Medical Centre Utrecht, Utrecht, The Netherlands.
authors.forename: Beatrijs L P
authors.initials: BL
authors.lastname: Bloemers
authors.forename: Grada M
authors.initials: GM
authors.lastname: van Bleek
authors.forename: Jan L L
authors.initials: JL
authors.lastname: Kimpen
authors.forename: Louis
authors.initials: L
authors.lastname: Bont
mesh_terms: D056704:Adaptive Immunity / Q000276:immunology; D015703:Antigens, CD / Q000032:analysis; D002648:Child; D002675:Child, Preschool; D003713:Dendritic Cells / Q000166:cytology; D004314:Down Syndrome / Q000276:immunology*; D005260:Female; D006801:Humans; D007113:Immunity, Innate / Q000276:immunology*; D016130:Immunophenotyping; D007223:Infant; D007694:Killer Cells, Natural / Q000166:cytology*; D007958:Leukocyte Count; D018950:Lipopolysaccharide Receptors / Q000032:analysis; D008297:Male; D009000:Monocytes / Q000276:immunology; D017452:Receptors, IgG / Q000032:analysis
chemical_list: D015703:Antigens, CD; D018950:Lipopolysaccharide Receptors; D017452:Receptors, IgG