Copy number variations of the IL-22 gene are associated with ankylosing spondylitis: A case-control study in Chinese Han population

IL-22 provides a new insight into the mechanisms of autoimmunity, and copy number variations (CNVs) are associated with autoimmune diseases. This study aims to explore the association of IL-22 gene CNVs with ankylosing spondylitis (AS) susceptibility. The copy numbers of IL-22 gene (2 fragments: IL-22_1, IL-22_2) were examined by AccuCopy™ methods in a cohort of 649 AS patients and 628 controls. Association of IL-22 CNVs and AS susceptibility was analyzed, and AS risk was estimated by Odds Ratio (ORs) and 95% confidence intervals (CIs), and the Benjamini-Hochberg method was applied to regulate the false discovery rate (FDR). We found one copy of IL-22 gene was significantly associated with AS [OR = 0.345, 95%CI (0.144, 0.827), P = 0.013, PFDR = 0.026] in the IL-22_2 fragment, and this association still exist after adjustment of age and sex [OR = 0.344, 95%CI (0.143, 0.825), P = 0.017, PFDR = 0.034]. In the stratification analysis by gender, the statistical difference was detected in males in the IL-22_2 fragment [OR = 0.306, 95%CI (0.121, 0.778), P = 0.009, PFDR = 0.018; adjusted OR = 0.306, 95%CI (0.120, 0.777), P = 0.013, PFDR = 0.026]. We suggest that IL-22 CNVs are associated with AS and that lower copy number might be a protective factor for AS, especially in male patients.