Expression of interleukin-18 in primary Sjögren syndrome and its potential mechanisms with disease: A systematic review and meta-analysis

BACKGROUND: Interleukin-18 (IL-18), an IL-1 family cytokine with potent ability to induce interferon gamma production and enhance Th1 response, was elevated in a group of autoimmune diseases including primary Sjögren syndrome (pSS). IL-18 dysregulation can contribute to the pathogenesis of these disorders by exerting function in innate and adaptive immunity. This study is aimed at comparing the level of IL-18 in pSS patients and explored the association between IL-18 and pSS. METHODS: Six databases, including PubMed, Web of Science, Embase, Ovid Medline, Scopus and China National Knowledge Infrastructure, were searched. The quality of the included studies was assessed using the Newcastle-Ottawa Scale criteria. We analyzed IL-18 concentrations in the serum and tear of pSS patients and healthy controls (HCs), and review the potential mechanism between IL-18 and pSS. RESULTS: Eleven articles were included in this study, which reported IL-18 levels in serum and tear of pSS patients and HCs. IL-18 levels in pSS patients were significantly higher than those in HCs (standard mean difference = 1.28, 95% confidence interval 0.75-1.82, P < .001), with substantial heterogeneity (I2 = 90%, P < .001) among the studies. The level of IL-18 in serum was analyzed separately and was also higher than those in HCs (standard mean difference = 1.28, 95% confidence interval 0.68-1.88, P < .001), with significant heterogeneity (I2 = 91%, P < .001). Apart from that, the potential pathogenesis of pSS was concluded comprehensively. CONCLUSION: IL-18 abundance was evidently elevated in pSS patients and can thus likely be used as a reliable biomarker to monitor and track the progression of pSS, and further to become a good target for treatment of pSS patient.