Interleukin 6 (IL-6) is a multifunctional cytokine secreted locally by a variety of cell types including T cells, B cells, monocytes/macrophages, endothelial cells, fibroblasts, hepatocytes, keratinocytes and astrocytes etc. IL-6 is up-regulated upon the binding of Toll-like receptors to antigen pattern ligands and by mitogenic stimulation during infection, acute phase reaction, trauma (especially burns) and malignancies. IL-6 secretion is significantly increased during physical excises. Also known as B-cell stimulatory factor-2 (BSF-2), IL-6 is an important cytokine for the differentiation of B-cells into immunoglobulin-secreting cells. In addition, IL-6 has been found to increase the number of platelets, influences cytotoxic T cell differentiation and activation, stimulate the differentiation and survival of neuronal cells, stimulate osteoclast formation, and induce terminal differentiation of M1 myeloid leukemic cells. IL-6 also stimulates the growth of hybridomas, plasmacytomas, myelomas, sarcomas, carcinomas, EBV-transformed B cells, keratinocytes, and mesangial cells. To melanoma cells and a few other cancer cells, IL-6 seemed to have an inhibitory effect.