Interleukin 6 as a therapeutic target in systemic-onset juvenile idiopathic arthritis.

PURPOSE OF REVIEW Systemic-onset juvenile idiopathic arthritis is a severe and steroid-dependent disease that sometimes progresses to a fatal disease, macrophage activation syndrome. The investigation of proinflammatory cytokine levels revealed the increases of interleukin 6 in serum of systemic-onset disease. To avoid the disease progression and the adverse events of high-dose corticosteroids, it might be a reasonable treatment strategy to inhibit the formation of interleukin 6/interleukin 6 receptor complex to block the binding to gp130 receptor, a biologically active receptor for interleukin 6. RECENT FINDINGS Continuously elevated levels of interleukin 6 in serum may play an important role in manifesting the clinical symptoms and signs of systemic-onset juvenile idiopathic arthritis, including spiking fever, rash, arthritis, and serositis. The characteristic fever spikes parallel interleukin 6 levels. A long-term exposure of high levels of interleukin 6 brings children severe growth impairment, which was strongly suggested by the recent establishment of interleukin 6 transgenic mice. SUMMARY This review will provide the evidences of the relation between the imbalance of interleukin 6 homeostasis and systemic-onset juvenile idiopathic arthritis. Also reviewed will be the author's recent trials of anti interleukin 6 receptor antibody, named temporally as MRA, for children with acute systemic disease intractable to long-term, high-dose, corticosteroid therapy. MRA would be a therapeutic modality for children with systemic-onset juvenile idiopathic arthritis intractable to high-dose corticosteroids.