Proposed model for the role of periodontal inflammation in rheumatoid arthritis (RA). Periodontal inflammation is associated with a chemical change in supragingival bacteria caused by an enzyme released as part of an immune response mechanism known as NETosis. This chemical change ‘decorates’ bacterial antigens with a molecular tag. Periodontitis and inflammation can cause breaches of the mucous membrane lining inside the mouth, releasing the tagged bacterial antigens into the blood. As a result, antibodies that target these molecular tags are activated, and they bind or trap the tagged antigens, forming molecules known as immune complexes. Immune complexes and plasmablasts deposit in joint tissue, also known as synovium, and contribute to its inflammation. Repeated episodes of oral bacteremia cause a heightened autoimmune response, affecting join tissue.