title: Elevation of plasma osteopontin concentration is correlated with disease activity in patients with systemic lupus erythematosus.
abstract: BACKGROUND
  Osteopontin (OPN) is an extracellular matrix cell adhesion phosphoprotein with immunological activities including stimulation of macrophage chemotaxis, T-helper type 1 lymphocyte response and B-cell antibody synthesis. Overexpression of OPN has been associated with the development of the autoimmune/lymphoproliferative syndrome.
  
  
  METHODS
  We measured the plasma concentration and ex vivo production of OPN, and the plasma proinflammatory IL-18 concentration in 54 SLE patients with or without renal impairment (RSLE group and SLE group, respectively) and 26 sex- and age-matched control (NC) subjects using an enzyme-linked immunoabsorbent assay.
  
  
  RESULTS
  Plasma OPN concentrations were significantly higher in RSLE and SLE patients than in the NC group (both P<0.001). Increase in OPN concentration correlated positively and significantly with SLEDAI score in all SLE patients (r = 0.308, P = 0.023). The ex vivo production of OPN upon mitogen activation of peripheral blood mononuclear cells was significantly higher in the RSLE and SLE groups than in the NC group (both P<0.001). In RSLE patients, plasma OPN concentration showed a significant positive correlation with proinflammatory cytokine IL-18 concentration (r = 0.404, P = 0.037).
  
  
  CONCLUSIONS
  The above results suggest that the production of OPN is associated with the inflammatory process and SLE development, and may serve as a potential disease marker of SLE.
authors.affiliation: Department of Chemical Pathology, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong.
authors.forename: C K
authors.initials: CK
authors.lastname: Wong
authors.forename: L C W
authors.initials: LC
authors.lastname: Lit
authors.forename: L S
authors.initials: LS
authors.lastname: Tam
authors.forename: E K
authors.initials: EK
authors.lastname: Li
authors.forename: C W K
authors.initials: CW
authors.lastname: Lam
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D020382:Interleukin-18 / Q000097:blood; D008180:Lupus Erythematosus, Systemic / Q000097:blood*; D008181:Lupus Nephritis / Q000097:blood; D008297:Male; D008875:Middle Aged; D053495:Osteopontin; D012720:Severity of Illness Index; D012795:Sialoglycoproteins / Q000096:biosynthesis / Q000097:blood*
chemical_list: D015415:Biomarkers; D020382:Interleukin-18; C506895:SPP1 protein, human; D012795:Sialoglycoproteins; D053495:Osteopontin