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Introduction: The purpose of this study was the evaluation of synovial effusion (SE), synovial fluid (SF) and synovial tissue (ST) biomarkers in relation to disease activity indexes to assess the response to intraarticular (IA) tumor necrosis factor (TNF)-α blockers in psoriatic arthritis (PsA)., Methods: Systemic and local disease activity indexes (disease activity score (DAS); the Ritchie articular index (mRAI), erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP); Thompson articular (THOMP) and joint articular (KJAI)-Index ) and ST samples were assessed at baseline, throughout treatment, and during the follow-up in 14 patients affected with PsA who underwent IA injections (0.5 ml to 12.5 mg) in the knee joint of etanercept (E) or placebo (P) once every two weeks for a 10-week period. Total SF white blood cell (WBC) counts (WBC/μl) and SF cytokine/chemokine (CK/CCK) levels were measured before IA-E at baseline, after IA-E, and as long as there were adequate amounts of SF for knee aspiration (post). Characterization of synovial mononuclear cell infiltration and synovial vessels was carried out in 8 out of 14 knees by staining serial sections of synovial tissue biopsies for CD45, CD3, CD68, CD31 and CD105., Results: At baseline, CRP and/or ESR were significantly correlated with SF-CK (interleukin- (IL-)1β, IL-1Ra, IL-6, IL-8) and CCK (CCL3). Post-IA injections, there was a decrease in SE in the knees in which aspiration following IA-E injection was possible as well as a significant reduction in SF WBC/μl and in SF-CK (IL-1β, IL-1Ra, IL-6 and IL-22). Pre- and post-IA-E injections, there were significant correlations between ST markers and SF-CK (IL-1β with CD45; IL-1β and IL-6 with CD31) and between SF-CCK (CCL4 and CCL3 with CD3). At the end of the study, there was a significant reduction in disease activity indexes (CRP, DAS, RAI, THOMP, KJAI) as well as in the ST markers (CD45; CD3)., Conclusions: Synovial effusion regression is a reliable indicator of the response to IA TNF-α blockers in PsA patients as it is confirmed by the correlation between SF biomarkers to disease activity and synovial tissue inflammation.

Associations between rheumatoid arthritis (RA) susceptibility and polymorphism in multiple immunoregulatory genes suggest a role of altered T cell function in the disease. The growing relevance of the oxidative stress in RA synovitis, which results in a number of T cell signalling abnormalities, is reinforced by the demonstration of a direct NO inducing activity through the shared epitope of the HLA class II molecules HLA-DRbeta1, with secondary lymphocytes oxidative damage. Direct T cell/macrophage contact-dependent activation, one of the driving mechanisms of synovitis, is mediated by co-stimulatory molecules as well as cell membrane cytokines and may also result in an impaired suppressive function of T regulatory cells (Treg) in RA joints. The fusion of CTLA4 extracellular binding domain to the Fcgamma1 allows to obtain a soluble CTLA4 receptor, the dimeric recombinant human fusion protein abatacept (CTLA4-Ig). The improved knowledge of the CTLA4-B7 co-stimulation regulatory mechanisms by signals delivered into DCs and Tregs provides multiple potential targets for the abatacept treatment. CTLA4-Ig shows the capacity, either ex vivo or in vivo, to interrupt at multiple steps the ongoing inflammatory and destructive process, and to concur in restoring the immunoregulatory balance in RA.