During gingivitis, the host is able to withstand microbes but, if periodontitis occurs, the existing equilibrium between the immune response and subgingival microbes gets altered, leading to uncontrolled inflammation characterized by the production of a high level of inflammatory intermediates, such as IL-1, IL-6, IL-17, and TNF-α and low levels of IL-10 inside periodontal tissues [31]. The gene discussed is IL17A; the disease is periodontitis.