BACKGROUND:The inflammatory cytokines,produced by synovial cells and invaded monocytes/macrophages and lymphocytes in synovial tissues of rheumatoid arthritis(RA),play a major role in rheumatoid synovial pathology.Interleukin(IL)-17,a recently found inflammatory cytokine,associates with many autoimmune diseases.OBJECTIVE:To detect IL-17 level Levels of interleukin-17 in serum of rats with collagen-induced arthritis(CIA),to study the relationships among IL-17 and the arthritis index,IL-1?,tumor n?ecrosis factor?(TNF-?),as well as matrix meralloproteinase 3(MMP-3).DESIGN,TIME AND SETTING:A randomized controlled animal trial was performed in the Immunology Laboratory of Medical College of Dalian University from March to August 2008.MATERIALS:Fifty female,inbred Wistar rats,aged 4-6 weeks,with average weight of(180?15) g.METHODS:Forty out of 50 rats were randomly selected for establishing CIA models.The other 10 rats were regarded as the normal control group.Rats in CIA group were injected intradermally 200 ?L emulsified type-II collagen at the base of the tail after model preparation.At day 7,a second boosted injection of emulsified CII in 100 ?L was administered at the base of the tail.The rats in normal controls were injected with the same dose of saline.MAIN OUTCOME MEASURES:Paw swelling was observed at 24 hours after immunization;The levels of IL-17,IL-1?,?T?NF-? a?nd MMP-3 were examined by ELISA;The inflammatory index of CIA rats was observed.RESULTS:The levels of IL-17,IL-1?,TNF-?,as well as MMP-3 in the CIA group was greater than that of the control group(all P