title: Interleukin-10 functions as an antiinflammatory cytokine in rheumatoid synovium.
abstract: OBJECTIVE
  Interleukin-10 (IL-10) is an antiinflammatory cytokine that has been shown to play a role in rheumatoid arthritis (RA). We therefore investigated the effects of IL-10 on the function and phenotype of synovial fluid mononuclear cells (SFMC) derived from patients with RA. In addition, we studied the production of IL-10 in rheumatoid joints, and the role of endogenous IL-10 in the regulation of SFMC function.
  
  
  METHODS
  The presence of IL-10 in rheumatoid joints was studied using IL-10-specific enzyme-linked immunosorbent assay (ELISA) and reverse transcriptase- polymerase chain reaction (RT-PCR) techniques. The effects of recombinant human IL-10 or neutralizing anti-IL-10 monoclonal antibodies (MAbs) on both cytokine production and phenotype of SFMC were evaluated using cytokine-specific ELISAs and flow cytometry. The effect of IL-10 on proliferation of SFMC was determined by incorporation of tritiated thymidine.
  
  
  RESULTS
  IL-10 was detected by ELISA in 22 of 23 SF samples, and was spontaneously produced by cultured SFMC. IL-10 messenger RNA was detectable in all 8 SFMC samples, as determined by RT-PCR. Neutralization of endogenously produced IL-10 by anti- IL-10 MAbs resulted in increased production of IL-1 beta, tumor necrosis factor alpha (TNF alpha), and granulocyte- macrophage colony-stimulating factor (GM-CSF) by SFMC, and in enhanced proliferation of SFMC. In particular, the production of TNFalpha was dramatically increased by anti-IL-10 MAbs. Moreover, the expression of HLA-DR molecules by SF macrophages was increased, and the expression of CD16 was decreased by anti-IL-10 MAbs. In contrast, addition of recombinant IL-10 significantly decreased the production of IL-1 beta, TNF alpha, and GM-CSF by SFMC, and decreased spontaneous and IL-2-induced proliferation of SFMC. Finally, IL-10 decreased HLA-DR expression and increased the expression of the Fc gamma receptors, CD16 and CD64, by SF macrophages.
  
  
  CONCLUSIONS
  These data indicate that endogenously produced IL-10 functions as an immunoregulatory molecule in rheumatoid synovium. Importantly, exogenous IL-10 has potent antiinflammatory effects on SFMC, suggesting that IL-10 may be useful in the treatment of patients with RA.
authors.affiliation: Turku University, Finland.
authors.forename: P
authors.initials: P
authors.lastname: Isomaki
authors.forename: R
authors.initials: R
authors.lastname: Luukkainen
authors.forename: R
authors.initials: R
authors.lastname: Saario
authors.forename: P
authors.initials: P
authors.lastname: Toivanen
authors.forename: J
authors.initials: J
authors.lastname: Punnonen
mesh_terms: D000328:Adult; D000368:Aged; D000893:Anti-Inflammatory Agents / Q000276:immunology*; D000911:Antibodies, Monoclonal; D001172:Arthritis, Rheumatoid / Q000276:immunology*; D001483:Base Sequence; D002455:Cell Division / Q000276:immunology; D016207:Cytokines / Q000096:biosynthesis / Q000276:immunology; D005260:Female; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000096:biosynthesis; D006684:HLA-DR Antigens / Q000276:immunology; D006801:Humans; D007375:Interleukin-1 / Q000096:biosynthesis; D016753:Interleukin-10 / Q000235:genetics / Q000276:immunology* / Q000494:pharmacology; D007592:Joint Diseases / Q000276:immunology; D008264:Macrophages / Q000166:cytology / Q000276:immunology / Q000502:physiology; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D015345:Oligonucleotide Probes; D012333:RNA, Messenger / Q000032:analysis; D013583:Synovial Membrane / Q000166:cytology / Q000276:immunology* / Q000503:physiopathology; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
chemical_list: D000893:Anti-Inflammatory Agents; D000911:Antibodies, Monoclonal; D016207:Cytokines; D006684:HLA-DR Antigens; D007375:Interleukin-1; D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D016178:Granulocyte-Macrophage Colony-Stimulating Factor