title: T cells and mast cells as a major source of interleukin-13 in atopic dermatitis.
abstract: BACKGROUND
  Interleukin (IL)-13 is a T-cell-derived cytokine that shares several functions with IL-4, including the induction of immunoglobulin E synthesis. Recent studies suggest that cytokines expressed locally in the skin play several critical roles in atopic dermatitis (AD), however, little is known about the role of IL-13 in AD lesions.
  
  
  OBJECTIVE
  The present study was designed to characterize the involvement of IL-13 in AD in the skin and peripheral blood mononuclear cells (PBMC).
  
  
  METHODS
  Using lesional and nonlesional skin from adult AD patients and normal skin from healthy volunteers, we performed RT-PCR, in situ RT and immunostaining to determine the IL-13 expression at the mRNA and protein levels. The actual numbers of IL-13 expressing cells in biopsy specimens were counted under the microscope. IL-13 mRNA expression in PBMC from AD patients and healthy volunteers was examined by RT-PCR analysis.
  
  
  RESULTS
  IL-13 mRNA expression was detected by RT-PCR in lesional and nonlesional skin and in PBMC from AD patients, but not in normal skin or PBMC from healthy volunteers. In AD lesional skin, numerous IL-13 mRNA-positive cells were demonstrated by in situ RT, and similar numbers of IL-13-positive cells were also detected immunohistochemically. Smaller numbers of IL-13-positive cells were observed in AD nonlesional skin and in normal skin. The differences in the numbers of IL-13-expressing cells between lesional and nonlesional skin were statistically significant. Double immunostaining revealed that IL-13 was produced in approximately 40% of T cells and 20% of mast cells in AD lesional skin, suggesting that T cells and mast cells are major sources of IL-13 in AD lesions.
  
  
  CONCLUSIONS
  IL-13 may play a local as well as a systemic role in the development of AD lesions.
authors.affiliation: Department of Dermatology, St. Marianna University School of Medicine, Kawasaki, Japan. m2mizo@marianna-u.ac.jp
authors.forename: Wataru
authors.initials: W
authors.lastname: Obara
authors.forename: Yoko
authors.initials: Y
authors.lastname: Kawa
authors.forename: Chisei
authors.initials: C
authors.lastname: Ra
authors.forename: Kusuki
authors.initials: K
authors.lastname: Nishioka
authors.forename: Yoshinao
authors.initials: Y
authors.lastname: Soma
authors.forename: Masako
authors.initials: M
authors.lastname: Mizoguchi
mesh_terms: D000328:Adult; D017252:CD3 Complex / Q000032:analysis; D003876:Dermatitis, Atopic / Q000276:immunology* / Q000473:pathology; D005260:Female; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood; D007150:Immunohistochemistry; D018793:Interleukin-13 / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008407:Mast Cells / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012867:Skin / Q000473:pathology; D013601:T-Lymphocytes / Q000378:metabolism*
chemical_list: D017252:CD3 Complex; D018793:Interleukin-13; D012333:RNA, Messenger; D007073:Immunoglobulin E