Abstract: PURPOSE: To investigate the immunopathology and immunomodulatory roles of interleukin-12 (IL-12) in periodontal disease. METHODS: Ninety-eight patients with chronic periodontitis from January 2016 to January 2019 were enrolled and divided into mild group (30 cases), moderate group (35 cases) and severe group (33 cases) according to the severity of periodontitis; meanwhile, 30 healthy subjects who underwent periodontal examination in our hospital were selected as the control group. Clinical periodontal indicators including probing depth(PD), attachment loss(AL), plaque index(PLI), bleeding index(BI), Th cell expression (Th1, Th2, Th17) in peripheral blood, IL-12 levels in gingival crevicular fluid (GCF) and serum were measured. SPSS 20.0 software package was performed to analyze the correlation between IL-12 levels in GCF and serum and Th1, Th2, Th17, PD, AL, PLI, and BI. RESULTS: The differences of PD, PLI and BI among the groups were statistically significant(P<0.05). The levels of PD, PLI and BI in the mild, moderate and severe group were significantly higher than those in the control group (P<0.05). The difference of AL index among mild, moderate and severe group was statistically significant(P<0.05). The PD, AL, PLI, and BI in the moderate and severe group was significantly higher than those in the mild group(P<0.05), and the severe group was significantly higher than the mild group(P<0.05). Th1, Th2 and Th17 were significantly higher in the mild, moderate and severe group than in the control group(P<0.05); the moderate, severe group was significantly higher than the mild group in terms of Th1, Th2 and Th17 (P<0.05), and the severe group was significantly higher than the moderate group (P<0.05). The IL-12 levels in GCF and serum of the mild, moderate, and severe groups were significantly higher than those of the control group (P<0.05); IL-12 levels in the the moderate and severe groups were significantly higher than those in the mild group (P<0.05), and the IL-12 were significantly higher in the severe group than in the moderate group (P<0.05); IL-12 was positively correlated with PD, AL, PLI, BI, Th1, Th2 and Th17(P<0.05). H-E staining showed there were fewer lymphocytes in the mild group, more lymphocytes in the moderate group, and dense lymphocytes in the severe group with significant hemorrhage in intercellular mesenchyme. The IL-12 protein positive staining results were expressed in gingival tissue lymphocyte pulp with significant brown observed. The positive staining of IL-12 protein in the gingival tissues in the mild, moderate and severe group was significantly higher than in the control group, and the staining was aggravated with mild, moderate and severe inflammatory changes. CONCLUSIONS: IL-12 is involved in the immunoregulatory mechanism of periodontal disease and may be a key pro-inflammatory cytokine in the development of periodontitis.

Key words: Chronic Periodontitis, Interleukin-12, Immunopathology, Immune regulation