The selection of cytokines and enzymes to be tested was based on their roles in immune response; IL-8, a chemoattractant cytokine, induces the infiltration of neutrophils and the release of other inflammatory cytokines such as IL-6 in periodontal tissues [31], IL-34 contributes to osteoclastogenesis in periodontitis [32], and IL-10, an anti-inflammatory and immunosuppressive cytokine, protects against tissue destruction via inhibiting MMPs and receptor activator for nuclear factor-kB (RANK) systems [33]. This evidence concerns the gene TNFRSF11A and periodontitis.