title: Enhanced expression of interleukin-18 receptor alpha chain by CD4+ T cells in sarcoidosis.
abstract: OBJECTIVE
  To investigate the expression of interleukin-18 receptor alpha chain (IL-18Ralpha) in BAL and peripheral blood (PB) T cells in patients with sarcoidosis compared with control subjects, to evaluate the relationship between the expression and clinical manifestations, and to clarify the mechanisms of altered expression.
  
  
  METHODS
  The study subjects consisted of 21 patients with sarcoidosis and 8 normal control subjects. The expression of IL-18Ralpha was examined by flow cytometry.
  
  
  RESULTS
  The proportions of BAL CD4+ and PB CD4+ T cells expressing IL-18Ralpha were significantly increased in patients with sarcoidosis compared to control subjects. BAL CD4+ T cells expressed IL-18Ralpha in a higher proportion than did paired CD8+ T cells in patients with sarcoidosis but not in control subjects. Greater proportions of BAL CD4+ T cells and BAL CD8+ T cells than of their PB counterparts expressed IL-18Ralpha in both patients and control subjects. CD4+ T cells were more sensitive to the induction of IL-18Ralpha by cytokines in vitro, such as interleukin (IL)-2, IL-12, and tumor necrosis factor-alpha than were CD8+ T cells. Increased expression of IL-18Ralpha by BAL T cells commonly observed in patients and control subjects was associated with the expansion of CD45RO+ cells in BAL T cells. However, there were no significant correlations between the expression of IL-18Ralpha by any cell populations and BAL findings, serum angiotensin-converting enzyme activities, radiograph stages, or clinical courses.
  
  
  CONCLUSIONS
  The overexpression of IL-18Ralpha predominantly by CD4+ T cells in sarcoidosis emphasizes crucial roles played by T-helper type 1 cells in the IL-18/IL-18Ralpha system in sarcoidosis.
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Yanqiu
authors.initials: Y
authors.lastname: Zhou
authors.forename: Etsuro
authors.initials: E
authors.lastname: Yamaguchi
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Fukui
authors.forename: Satoshi
authors.initials: S
authors.lastname: Konno
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Maeda
authors.forename: Koji
authors.initials: K
authors.lastname: Kimata
authors.forename: Masaharu
authors.initials: M
authors.lastname: Nishimura
mesh_terms: D001992:Bronchoalveolar Lavage Fluid / Q000276:immunology; D018791:CD4 Lymphocyte Count; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002478:Cells, Cultured; D005434:Flow Cytometry; D006801:Humans; D053727:Interleukin-18 Receptor alpha Subunit; D018123:Receptors, Interleukin / Q000378:metabolism*; D053724:Receptors, Interleukin-18; D012016:Reference Values; D012507:Sarcoidosis / Q000276:immunology*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology
chemical_list: C508572:IL18R1 protein, human; D053727:Interleukin-18 Receptor alpha Subunit; D018123:Receptors, Interleukin; D053724:Receptors, Interleukin-18