Interleukin-17 Immunity in Pediatric Crohn Disease and Ulcerative Colitis

Objective: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.Methods: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.Results: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.Conclusions: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.