Interleukin‐17 Immunity in Pediatric Crohn Disease and Ulcerative Colitis

Abstract

The present understanding of inflammatory bowel disease pathogenesis mainly relies on studies of adult patients. Therefore, we studied the balance between T-effector and regulatory cells in pediatric inflammatory bowel disease. Quantitative polymerase chain reaction and immunohistochemistry served to quantify the expression of immunological markers in mucosal biopsies and flow cytometry analysis was used in peripheral blood mononuclear cells. Colonic interleukin (IL)-17+, IL-22, and IL-6 mRNA upregulation and increase in the number of colonic IL-17 cells were demonstrated in both Crohn disease (CD) and ulcerative colitis (UC). Likewise, colonic forkhead box P3 (FOXP3+) mRNA expression and the number of colonic FOXP3 cells were increased both in CD and in UC and were accompanied in CD also with increased numbers of FOXP3+CD25 High CD4 cells in peripheral blood. Ileal relation of IL-17/CD4 cells was increased only in CD. We showed activation of colonic IL-17/IL-22 axis and upregulation of FOXP3 to occur both in pediatric CD and in UC, indicating shared immunological characteristics. Upregulation of IL-17 was restricted to colon in UC, but existed in the ileum and in the colon in active CD.