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Mechanism of Action: Tocilizumab binds specifi cally to both soluble and membrane-bound IL-6 receptors and has been shown to inhibit IL-6-mediated signaling through these receptors. IL-6 is a pleiotropic pro-infl ammatory cytokine produced by a variety of cell types including T-and B-cells, lymphocytes, monocytes and fi broblasts. IL-6 has been shown to be involved in diverse physiological processes such as T-cell activation, induction of immunoglobulin secretion, initiation of hepatic acute phase protein synthesis, and stimulation of hematopoietic precursor cell proliferation and differentiation. IL-6 is also produced by synovial and endothelial cells leading to local production of IL-6 in joints affected by infl ammatory processes such as rheumatoid arthritis.