Other suggested effects are: ability to compete with pathogens for epithelial cell adhesion (10), a reduction in the production of proinflammatory cytokines (TNF-α, IL-1β, IL-17), (20) a reduction in MMP-8 expression, which is the main collagenase involved in chronic periodontitis, and an increase of TIMP-1, which is a modulating factor of MMP activity. This evidence concerns the gene IL17A and periodontitis.