Background/aim To investigate the contribution of muscle tissue-derived cytokines in dermatomyositis (DM). Materials and methods Muscle homogenates were prepared from deltoid muscle biopsy specimens of 10 patients with DM and eight controls with no pathological signs of myopathy. Interleukin (IL)-4, interferon (IFN)-γ and IL-17 levels were evaluated by enzyme-linked immunosorbent assay (ELISA) and immunoblotting analysis. Muscle strength grades were recorded. Results Patients with DM showed significantly elevated muscle tissue IL-4 and IFN-γ levels, whereas IL-17 levels were comparable between patients with DM and controls. Immunoblotting studies confirmed ELISA results. In DM muscle specimens, IL-4 and IFN-γ levels were positively correlated, while no correlation was observed between IL-17 and the other two cytokines. Moreover, IL-4 and IFN-γ levels were significantly negative correlated with muscle strength grades for the deltoid muscle. Conclusion Our results confirm the involvement of T helper (Th) 1-type and Th2-type immunity in DM pathogenesis. Muscle tissue appears to contribute to muscle weakness in DM by producing inflammatory cytokines.
