Altered serum profile of the interleukin-22 system in inflammatory bowel disease.

Background and Aim: Interleukin-22 (IL-22), plays a vital role in the mucosal repair of inflammatory bowel disease (IBD). Serum levels of IL-22 and IL-22 binding protein (IL-22BP), a soluble inhibitory IL-22 receptor, were measured in patients with IBD to investigate the profile of IL-22 in the systemic circulation. Methods: Blood samples from 92 healthy subjects, 98 patients with ulcerative colitis (UC), and 105 patients with Crohn's disease (CD) were analyzed for serum levels of IL-22, IL-22BP, human beta-defensin 2 (hBD-2), and serum inflammatory parameters. Disease activity was assessed by the partial Mayo score and Harvey-Bradshaw index for UC and CD, respectively. Results: Serum IL-22 level was lower in UC (P< 0.001) and CD (P< 0.001) vs control and its decrease was more pronounced in CD than in UC (P = 0.019). Serum IL-22BP level was lower in UC (P< 0.001) and CD (P< 0.001) vs control and correlated with inflammatory parameters (albumin and C-reactive protein (CRP) in UC; hemoglobin, albumin, and CRP in CD). Serum IL-22/IL-22BP ratios were higher in UC (P = 0.009) vs control and correlated with inflammatory parameters (albumin and CRP). Serum hBD-2 level was higher only in CD (P = 0.015) but did not correlate with serum IL-22 levels, IL-22BP levels, IL-22/IL-22BP ratios, or inflammatory parameters. Conclusions: Dysregulation of the IL-22 system in the blood may play a role in the pathogenesis of IBD. Further studies are needed to understand the pathogenic and clinical significance of the blood IL-22 system in IBD.