Cytokines play a critical role in the pathogenesis of arthritis. The aim of this study was to compare the amounts of IL-1 alpha, IL-1 beta, IL-4, IL-6, IL-8, IL-10, IL-12, TNF-alpha, TGF-beta 1 and IFN-gamma in the synovial fluid of 30 patients with rheumatoid arthritis (RA), 40 patients with osteoarthritis (OA) and 13 patients with seronegative spondylarthropathies (SpA).
Since some samples exhibited non-specific activities, all cytokines were measured by ELISA in the presence or absence of cytokine specific neutralizing antibodies.
Our data show that these cytokines can be detected in OA, RA and SpA. Compared to patients with OA, all cytokines were found in higher levels in patients with RA and SpA. Surprisingly, higher levels of IL-4, IL-10 and TGF-beta 1 were not associated with lower cytokine levels. In contrast, higher levels of IFN-gamma were associated with elevated monokine concentrations.
Our data indicate that the immunosuppressive effects of IL-4, IL-10 and TGF-beta 1 predicted from in vitro studies may not be active in vivo. Different monokine profiles could be observed in patients with IL-4 and/or IFN-gamma, indicating that the T cells involved in these diseases may have different immunoregulatory properties.