In RA and periodontitis, fibroblasts stimulated by activated immune cells32 produce various mediators of inflammation, cytokines (IL-1β, IL-6, TNF-α), chemokines (IL-8, CXCL10, CXCL11, CCL20), prostaglandin E2,35 matrix metalloproteinases (MMPs),32 and RANKL.32,36 Fibroblasts contribute directly to local joint damage, but they can also migrate between joints in RA, promoting inflammation in other joints and demonstrating the symmetric nature of the disease.37 This evidence concerns the gene IL1B and periodontitis.