title: Serum soluble interleukin 7 receptor is strongly associated with lupus nephritis in patients with systemic lupus erythematosus.
abstract: BACKGROUND
  The soluble form of the interleukin 7 receptor (sIL-7R) is produced by fibroblasts after stimulation with proinflammatory cytokines. Increased sIL-7R serum and synovial fluid levels were recently demonstrated in patients with rheumatoid arthritis.
  
  
  OBJECTIVE
  To investigate whether sIL-7R production is dysregulated in systemic lupus erythematosus (SLE), and whether this correlates with disease activity.
  
  
  METHODS
  Serum and urine sIL-7R concentrations were measured by ELISA, and sIL-7R quantitative PCR (qPCR) studies were performed in peripheral blood mononuclear cells (PBMCs). IL-7R, tumour necrosis factor α (TNFα), IL-1β and IL-17 immunostainings were performed on kidney sections.
  
  
  RESULTS
  sIL-7R concentrations were significantly higher in SLE sera than in controls, and correlated with SLE Disease Activity Index (SLEDAI) scores. Accordingly, serum sIL-7R levels were strongly raised in patients with nephritis. Moreover in patients with lupus nephritis, serum sIL-7R decreased upon treatment. sIL-7R gene expression in PBMCs was similar in patients with lupus nephritis and controls. By contrast, abundant perivascular IL-7R expression was seen in SLE kidney biopsy specimens, which was associated with expression of TNFα in the surrounding tissue.
  
  
  CONCLUSIONS
  Our data indicate that sIL-7R is a marker of SLE disease activity, especially nephritis. In contrast to conventional disease activity markers, sIL-7R is not produced by immune cells, but might instead reflect activation of tissue cells in the target organ.
authors.affiliation: Pôle de Recherche en Rhumatologie, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium.
authors.forename: Valérie
authors.initials: V
authors.lastname: Badot
authors.forename: Remco K M A C
authors.initials: RK
authors.lastname: Luijten
authors.forename: Joel A
authors.initials: JA
authors.lastname: van Roon
authors.forename: Geneviève
authors.initials: G
authors.lastname: Depresseux
authors.forename: Selda
authors.initials: S
authors.lastname: Aydin
authors.forename: Benoît J
authors.initials: BJ
authors.lastname: Van den Eynde
authors.forename: Frédéric A
authors.initials: FA
authors.lastname: Houssiau
authors.forename: Bernard R
authors.initials: BR
authors.lastname: Lauwerys
mesh_terms: D000328:Adult; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008180:Lupus Erythematosus, Systemic / Q000097:blood / Q000150:complications; D008181:Lupus Nephritis / Q000097:blood*; D008297:Male; D020395:Receptors, Interleukin-7 / Q000097:blood*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D020395:Receptors, Interleukin-7