title: Influence of blood and synovial fluid immune complexes of patients with rheumatoid arthritis on production of nitric oxide and growth and viability of chondrocytes.
abstract: OBJECTIVE
  To determine whether blood and synovial fluid (SF) immune complexes (IC) of patients with rheumatoid arthritis (RA) influence the production of nitric oxide (NO) and growth and viability of chondrocytes.
  
  
  METHODS
  IC were precipitated and IgM and IgG were determined in the precipitates by ELISA and nephelometry, respectively. Primary cultures of bovine articular chondrocytes were incubated with the IC precipitates. After 48 h NO was determined as nitrite. After 7 days, growth was determined by incorporation of tritiated thymidine and viability was detected by neutral red uptake.
  
  
  RESULTS
  Patient sera were positive in 8/12 for IgM IC and 9/12 for IgG IC, and 1/8 control sera was slightly positive for IgM IC. Seven of 12 SF samples were IgM IC and 10/12 IgG IC positive. With and without additional interleukin 1alpha (IL-1alpha) stimulation, NO production by chondrocytes was significantly higher with SF IC precipitates than with control serum precipitates (p = 0.03, p = 0.04, respectively). NO production by chondrocytes that were not stimulated with IL-1alpha was significantly increased with SF IC precipitates compared to RA serum IC precipitates (p = 0.03). SF IC significantly inhibited growth compared to control serum precipitates (p = 0.04) and RA serum IC (p = 0.012). Neutral red uptake by chondrocytes was significantly decreased when incubated with RA serum IC in comparison with control serum IC (p = 0.012) and SF IC (p = 0.006). With and without additional IL-1alpha stimulation, NO production by chondrocytes after incubation with SF derived IC was positively correlated to the Ritchie score (r = 0.8, r = 0.7, respectively) and the number of swollen joints (r = 0.8, r = 0.6, respectively).
  
  
  CONCLUSIONS
  These results support the hypothesis that, especially in active RA, SF derived IC stimulate NO production and inhibit chondrocyte growth.
authors.affiliation: Department of Immunology, Allergology and Rheumatology, University of Antwerp, Belgium.
authors.forename: A
authors.initials: A
authors.lastname: Verbruggen
authors.forename: L S
authors.initials: LS
authors.lastname: De Clerck
authors.forename: C H
authors.initials: CH
authors.lastname: Bridts
authors.forename: F C
authors.initials: FC
authors.lastname: Breedveld
authors.forename: W J
authors.initials: WJ
authors.lastname: Stevens
mesh_terms: D000936:Antigen-Antibody Complex; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000276:immunology*; D002455:Cell Division; D019902:Chondrocytes / Q000378:metabolism*; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis*; D013582:Synovial Fluid / Q000276:immunology*
chemical_list: D000936:Antigen-Antibody Complex; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D009569:Nitric Oxide