S100A9 and rheumatoid arthritis: In extracellular fluid, increased levels of S100A9/S100A8 etherodimer were reported in numerous inflammation-associated conditions, such as rheumatoid arthritis, Crohn’s Disease, colorectal cancer and in GCF (Gingival Crevicular Fluid) of patients suffering from gingivitis and periodontitis [30, 31].