Comparison of interleukin-21 levels and its correlation with clinical parameters among healthy individuals, chronic periodontitis, and aggressive periodontitis patients

BACKGROUND: Interleukin-21 (IL-21) has both anti- and pro-inflammatory roles associated with chronic inflammation. It causes tissue destruction by increasing pro-inflammatory cytokines and curbs the activity of certain immune cells that evoke an anti-inflammatory role. OBJECTIVES: The aim of this study was to compare IL-21 levels in gingival crevicular fluid among patients with generalized chronic periodontitis (GCP), aggressive periodontitis, and healthy gingiva (HG) and to correlate IL-21 levels with clinical parameters. METHODS: In this cross-sectional case-control study, 60 subjects were categorized into three groups: HG (n=20), generalized aggressive periodontitis (GAP; n=20), and GCP (n=20). IL-21 was measured using ELISA and results were correlated with clinical parameters including plaque index, gingival index, periodontal probing depth (PPD), and clinical attachment level (CAL). RESULTS: Mean IL-21 levels were 20.0±0.7 in HG, 25.9±0.9 in GCP, and 25.3±1.1 in GAP groups. Significant differences in IL-21 levels were found between HG versus GAP (P<0.05) and HG versus GCP (P<0.05). No statistically significant difference in IL-21 level was found between GCP versus GAP. IL-21 levels positively correlated with PPD (r=0.97) and CAL (r=0.93) in the GAP group and with PPD (r=0.92) and CAL (r=0.96) in the GCP group. CONCLUSION: Although periodontitis pathophysiology involves complex interplay between pro- and anti-inflammatory signaling, data on IL-21 revealed elevated levels in both GCP and GAP. Further longitudinal studies are required to characterize and determine the diagnostic value of IL-21 as a reliable biomarker in periodontal disease. RELEVANCE FOR PATIENTS: Although further longitudinal studies are necessary, IL-21 may serve as a potential inflammatory biomarker in screening for generalized chronic and aggressive periodontitis.