Cytokines in thyroid eye disease: potential for anticytokine therapy.

Interactions between between orbital fibroblasts and immunocompetent cells that infiltrate or reside within the orbit are thought to be important in the pathogenesis of thyroid eye disease (TED). These interactions are mediated primarily by cytokines; interferon-gamma, tumor necrosis factor-alpha, interleukin-1alpha and leukoregulin are of particular interest in this regard. These mediators induce or enhance the in vitro expression of immunomodulatory proteins in orbital fibroblasts, and stimulate proliferative and metabolic activities of these cells. The stimulation by particular cytokines of glycosaminoglycan synthesis in orbital fibroblasts is an important factor in the development of the clinical disease. A similarly important pathophysiological role for cytokines has been defined in rheumatoid arthritis. In this disease, the chronic erosive changes in the cartilage and bone of the joints result from cytokine-stimulated production of collegenases and other neutral proteases by synovial cells and articular chondrocytes. Advances in the understanding of the pathogenesis of rheumatologic joint disease has led to treatment trials aimed at immune-modulation, including trials of anticytokine therapy. Lessons learned in early clinical trials using these biological therapies in the treatment of rheumatoid arthritis can be applied to studies of similar agents in the treatment of TED.