Immunohistochemical Analysis of IL-19 and IL-24 Expression in Inflammatory Bowel Disease (IBD) Patients: Results From a Single Center Retrospective Study.

Background IL-19 and IL-24 induce proinflammatory cytokine production through the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway. The primary objective of this study was to investigate any changes in IL-19 and IL-24 expression between inflammatory bowel disease (IBD) patients and healthy controls, as well as before and after the initiation of biologics. The secondary objective was to investigate any relation between their expression and disease phenotype and activity.  Methods IL-19 and IL-24 expression was measured in intestinal tissue samples from 121 patients with moderate to severe IBD versus healthy controls using immunohistochemistry. Their expression was then measured 12 months after treatment on the patient group treated with biologics. The disease activity was measured before and after treatment using the Harvey Bradshaw Index (HBI) for Crohn's disease (CD) patients and the Mayo Score (MS) for ulcerative colitis (UC) patients. Data were analyzed using SPSS (IBM Inc., Armonk, New York).  Results IL-19 expression was raised in the IBD group versus healthy controls. In the CD group, the IL-19 expression was related with the disease activity score post-biologic treatment. IL-24 was also highly expressed in patients with active UC and CD and was increased post-treatment. Its expression in UC was statistically related with the MS. Conclusions IL-24 and IL-19 are key factors in IBD-related intestinal inflammation and this is one of the few human studies to suggest that. An immunosuppressive role of IL-24 was demonstrated in the UC group. A future use as biomarkers of disease activity and response to treatment might be feasible.