*Review* **Th17 Cells and the IL-23**/**IL-17 Axis in the Pathogenesis of Periodontitis and Immune-Mediated Inflammatory Diseases**

### **Kübra Bunte and Thomas Beikler \***

Department of Periodontics, Preventive and Restorative Dentistry, UniversityMedicalCentreHamburg-Eppendorf,20246Hamburg,Germany

 **\***Correspondence:t.beikler@uke.de;Tel.:+49-(0)-40-7410-52282;Fax:+49-(0)-40-7410-55168

Received: 23 May 2019; Accepted: 8 July 2019; Published: 10 July 2019

**Abstract:** Innate immunity represents the semi-specific first line of defense and provides the initial host response to tissue injury, trauma, and pathogens. Innate immunity activates the adaptive immunity, and both act highly regulated together to establish and maintain tissue homeostasis. Any dysregulation of this interaction can result in chronic inflammation and autoimmunity and is thought to be a major underlying cause in the initiation and progression of highly prevalent immune-mediated inflammatory diseases (IMIDs) such as psoriasis, rheumatoid arthritis, inflammatory bowel diseases among others, and periodontitis. Th1 and Th2 cells of the adaptive immune system are the major players in the pathogenesis of IMIDs. In addition, Th17 cells, their key cytokine IL-17, and IL-23 seem to play pivotal roles. This review aims to provide an overview of the current knowledge about the differentiation of Th17 cells and the role of the IL-17/IL-23 axis in the pathogenesis of IMIDs. Moreover, it aims to review the association of these IMIDs with periodontitis and briefly discusses the therapeutic potential of agents that modulate the IL-17/IL-23 axis.

**Keywords:** periodontitis; psoriasis; rheumatoid arthritis; Crohn's disease; ulcerative colitis; systemic lupus erythematosus; Sjögren syndrome; type 1 diabetes mellitus; cytokines; Th17 cells; interleukin-17; interleukin-23
