Estimation of Interleukin-21 Levels in Gingival Crevicular Fluid in Patients With Periodontal Health and Disease Following Non-surgical Periodontal Therapy: A Clinico-biochemical Study

Introduction

Periodontal disease is a poly-microbial disease that affects tooth-supporting tissues. Integral part of periodontal disease involves destruction of periodontal tissues that results from stimulation of the bacterial challenge to host immune-inflammatory response. Chronic periodontitis is the most common form of periodontal disease in adult population. The bacterial plaque biofilm is the primitive factor for periodontitis, but the majority of destruction of the periodontal tissues would eventually conclude from a sequence of immune-inflammatory reactions. As a result of cellular activation, inflammatory mediators include cytokines, chemokines etc. collectively contribute to tissue destruction and bone resorption. Cytokines can be grouped as Th1, Th2, Th17 and T regulatory (Treg) based on their expression pattern and effects on target cells or tissues.5 Classically, periodontal disease has been explained by Th1/Th2 pathway. Th1 cells are more frequently detected in the early stage of periodontal lesions suggesting that Th1 cells are associated with a protective response against bacterial infection whereas Th2 cells predominate in the later and advanced period of the disease, having a role in the destruction and progression of periodontal lesions. Alternative type of host response to pathogenic bacteria has been described by the IL-23/IL-17 pathway. This alternative pathway occurs when bacteria induce synthesis of IL-23/17 rather than IL-12, which plays a pivotal role in initiation and maintenance of inflammatory response. IL-23/17 pathway as compared to classical Th1/Th2 pathway is a much fine tuned cellular immune response that has a multitude of functions that bridges the innate and adaptive arm of the immune response.9 Th17 cytokines (IL-17, IL-21, IL-22, IL-6, Tumor necrosis factor {TNF}-a, etc.)8 participate in periodontal disease, but whether their dominant role is host-protective or destructive is questionable. These cytokines have not been elucidated at different inflammatory status in periodontitis.

IL-21 is a type-I cytokine, structurally it appears similar to IL-2, IL-4, and IL-15 proteins. IL-21 is principally composed by activated T cells, but it directs a vast spectrum of myeloid and lymphoid cells of the immune system, which facilitate IL-21 to modulate the acquired and innate immunity.10 IL-21 compete in the immunity against tumor cells11 and chronic viral infections,12 however, enormous accomplishment of IL-21 has been correlated with the advancement of immune inflammatory diseases in various organs.13 IL-21 is heighten in dermatological conditions like skin biopsies14 of patients with systemic lupus erythematosus, psoriasis, and atopic dermatitis. In addition, IL-21 interpretation correspond with the presence of Th17 cells in synovial fluid and peripheral blood of rheumatoid arthritis patients.

Role of IL-21 in inflammation has been extensively studied; the treatment aspect on its levels in periodontal diseases needs to be further explored. Therefore, in the light of the above findings, the investigators determine the levels of interleukin-21 (IL-21) in GCF from chronic gingivitis, chronic periodontitis and control patients before and after non-surgical periodontal therapy along with the co-relation of clinical parameters of periodontal tissues destruction.

MATERIAL AND METHODS: