IL-6 can alter the T helper cell phenotype programming [104]; it can stimulate B cells, NK cells, osteoclasts, and cancer cells [105] and is secreted by a variety of cells; among these are lymphocytes, macrophages, endothelial cells, epithelial cells, and fibroblasts; these then play a major role in autoimmune diseases, especially RA, in which increased levels of IL-6 are found in synovial fluid [106]. Here, IL6 is linked to rheumatoid arthritis.