A Systematic Review of Interleukin-17 in Oral Lichen Planus: From Etiopathogenesis to Treatment.

Lichen planus (LP) is a chronic autoimmune disease of skin and mucous membranes. World Health Organization has announced oral lichen planus (OLP) as a premalignant lesion. The exact etiology of OLP remains unknown; however, different mechanisms may be involved in its immunopathogenesis. The upregulation of cytokines, chemokines, and adhesion molecules is consistent with a persistent and erratic immunological response to OLP-mediated antigens generated by oral keratinocytes and innate immune cells. These molecules attract T cells, and mast cells to the disease site and regulate complex interactions among cells that lead to death of keratinocytes, degradation of basement membrane, and chronicity of the disease. It is believed that CD8+ and CD4+ T helper 1 (Th1) cells are the main lymphocytes involved in this process, although recent evidence suggests implication of other T helper subgroups, such as Th23, Th17, and regulatory T cells (Tregs), proposing a more complex cellular immunity process to be involved in its pathogenesis. The emphasis of this research review is on the function of IL-17 in the pathophysiology of OLP and how current discoveries may point to future treatment strategies. This research protocol will follow Preferred Reporting Items for Systematic Reviews (PRISMA 2020) checklist. An electronic search was conducted in PubMed, Scopus, Google Scholar, Embase, and Cochrane databases for articles published from 1960 to June 2022. Based on the eligibility criteria, 21 articles were enrolled. In comparison to healthy controls, the findings of this review demonstrated greater expression of IL-17 and Th-17 in the blood, saliva, and tissues of OLP and LP patients. Additionally, there was a strong link between the relative levels of IL-17 and IL-23 expression. Treatment with monoclonal antibodies against Th-17/Tc-17, IL-12/IL-23, and IL-23 would result in significant long-term improvement of LP symptoms.