Simultaneously, in response to bacterial colonization, immune system leukocytes release proinflammatory cytokines that are central to the progression of chronic periodontitis, including IL-1α, IL-1β, IL-6, IL-12, tumor necrosis factor (TNF)-α, as well as regulatory cytokines like IL-4, IL-1 receptor antagonist (RA), IL-10, and induced protein IP-10 [22,23,24]. This evidence concerns the gene IL4 and periodontitis.