title: Increased levels of circulating intercellular adhesion molecule 1 in the sera of patients with rheumatoid arthritis.
abstract: OBJECTIVE
  We sought to assess whether circulating levels of intercellular adhesion molecule 1 (ICAM-1) in patients with rheumatoid arthritis (RA) are elevated and correlate with clinical measures of disease activity and whether this ICAM-1 originates from the synovium.
  
  
  METHODS
  Circulating ICAM-1 (cICAM-1) levels were determined by sandwich enzyme-linked immunosorbent assay of serum from 61 RA, 18 osteoarthritis (OA), and 11 inflammatory arthritis (IA) patients. In addition, paired serum and synovial fluid samples were collected from 17 RA, 9 OA, and 4 IA patients. The stability of cICAM-1 was assessed by overnight incubation at 37 degrees C. Finally, the potential degradative effects of synovial fluid proteases were assessed by incubation of recombinant soluble ICAM-1 with patient synovial fluid.
  
  
  RESULTS
  RA sera contained significantly greater (P < 0.001) levels of cICAM-1 compared with RA synovial fluid and compared with sera or synovial fluid from the OA and IA patients. Circulating ICAM-1 levels were unaffected by overnight incubation at 37 degrees C and were unaffected by exposure to RA, OA, or IA synovial fluid. Serum levels of cICAM-1 demonstrated a weak, but significant (P < 0.05) correlation with the joint score and erythrocyte sedimentation rate in 25 RA patients treated with nonsteroidal antiinflammatory drugs.
  
  
  CONCLUSIONS
  The greatest elevations of cICAM-1 were seen in RA patient sera. In both RA and OA, synovial fluid cICAM-1 levels were consistently lower than serum levels, suggesting that cICAM-1 did not originate in the synovium. Because the production of cICAM-1 can be increased by cytokines (e.g., interleukin-1, tumor necrosis factor alpha), elevated levels of circulating ICAM-1 in RA may be reflective of systemic exposure to elevated cytokine levels.
authors.affiliation: University of Texas Southwestern Medical Center, Dallas 75235.
authors.forename: J J
authors.initials: JJ
authors.lastname: Cush
authors.forename: R
authors.initials: R
authors.lastname: Rothlein
authors.forename: H B
authors.initials: HB
authors.lastname: Lindsley
authors.forename: E A
authors.initials: EA
authors.lastname: Mainolfi
authors.forename: P E
authors.initials: PE
authors.lastname: Lipsky
mesh_terms: D000368:Aged; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000627:therapeutic use*; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000188:drug therapy; D015815:Cell Adhesion Molecules / Q000032:analysis* / Q000097:blood; D005260:Female; D006801:Humans; D018799:Intercellular Adhesion Molecule-1; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000097:blood* / Q000188:drug therapy; D012720:Severity of Illness Index; D013582:Synovial Fluid / Q000737:chemistry*; D013696:Temperature
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D015815:Cell Adhesion Molecules; D018799:Intercellular Adhesion Molecule-1