title: Evidence for a role of Langerhans cell-derived IL-16 in atopic dermatitis.
abstract: BACKGROUND
  The factors controlling infiltration of inflammatory cells into atopic dermatitis (AD) lesions remain to be fully explored. Recently, epidermal cells in lesional AD were reported to contain increased messenger (m)RNA levels of IL-16, a cytokine that induces chemotactic responses in CD4(+)T cells, monocytes, and eosinophils.
  
  
  OBJECTIVE
  We sought to determine the expression of IL-16 in epidermal cells in normal skin and skin from AD lesions and to investigate whether Langerhans cell (LC)-derived IL-16 may contribute to the initiation of atopic eczema.
  
  
  METHODS
  The cutaneous expression of IL-16 was investigated by in situ hybridization and immunohistochemistry. Expression of IL-16 was also investigated in freshly isolated LCs and in keratinocytes by intracellular cytokine staining, quantitative real-time RT-PCR, and ELISA.
  
  
  RESULTS
  Low levels of IL-16 mRNA, but no stored IL-16 protein, were detected in keratinocytes and LCs isolated from normal skin. Synthesis, storage, and secretion of IL-16 could be induced in LCs, but not keratinocytes, by activation with phorbol ester and ionomycin. In normal skin (n = 10) neither keratinocytes nor LCs expressed IL-16. In contrast, IL-16 was contained in approximately 40% of CD1a(+)LCs in patients with active AD (n = 16). IL-16 expression in LCs in patients with AD correlated with the number of infiltrating CD4(+)cells (r =.72, P =.0017) and was completely downregulated parallel to the clinical response of AD lesions to topical treatment with FK506.
  
  
  CONCLUSIONS
  LC-derived IL-16 may participate in the recruitment and activation of inflammatory cells in AD.
authors.affiliation: Department of Dermatology, Georg-August-University, Göttingen, Germany.
authors.forename: Kristian
authors.initials: K
authors.lastname: Reich
authors.forename: Sabine
authors.initials: S
authors.lastname: Hugo
authors.forename: Peter
authors.initials: P
authors.lastname: Middel
authors.forename: Volker
authors.initials: V
authors.lastname: Blaschke
authors.forename: Andrea
authors.initials: A
authors.lastname: Heine
authors.forename: Carsten
authors.initials: C
authors.lastname: Gutgesell
authors.forename: Ruth
authors.initials: R
authors.lastname: Williams
authors.forename: Christine
authors.initials: C
authors.lastname: Neumann
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D003876:Dermatitis, Atopic / Q000188:drug therapy / Q000209:etiology* / Q000276:immunology; D006801:Humans; D019410:Interleukin-16 / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D007801:Langerhans Cells / Q000502:physiology*; D012867:Skin / Q000378:metabolism; D016559:Tacrolimus / Q000627:therapeutic use
chemical_list: D000911:Antibodies, Monoclonal; D019410:Interleukin-16; D016559:Tacrolimus