IL-17 enhances bone destruction in rheumatoid arthritis, but IL-17 signaling through IL-17 receptor exerts bone protective effect on periodontal bone loss because it provides antimicrobial defense against periodontal organisms like P. gingivalis [12] and decreases alveolar bone resorption due to defective neutrophil chemotaxis [33]. The gene discussed is IL17A; the disease is rheumatoid arthritis.