Foxp3+ Regulatory T Cells, Th17 Effector Cells, and Cytokine Environment in Inflammatory Bowel Disease

Abstract

Inflammatory bowel disease (IBD) is thought to result from an aberrant immune response. Inflammation in IBD may be caused by the loss of homeostasis between CD4⁺ CD25^high Foxp3⁺ regulatory cells (T _reg) and proinflammatory Th17 cells. The aim of this study was to investigate T _reg and Th17 cells in the peripheral blood and intestinal mucosa of IBD patients and to assess the mucosal cytokine environment. T _reg and Th17 cells were measured in peripheral blood of 63 IBD patients and 28 controls by flow cytometry. Forkhead box p3 (Foxp3), interleukin (IL)-17a, IL-1β, IL-6, IL-21, IL-23, and transforming growth factor (TGF)-β mRNA were analyzed using real-time reverse transcription polymerase chain reaction in intestinal biopsies of 24 IBD and 18 control subjects. A decrease in T _reg and increase in Th17 cells was observed in the peripheral blood of IBD patients. When measured in the same patient and expressed as a ratio, a significant decrease in T _reg/Th17 ratio was observed in IBD. Elevated expression of Foxp3, IL-17a, IL-1β, and IL-6 was observed in the mucosa of IBD patients, while TGF-β was only elevated in ulcerative colitis. IBD is associated with a reduced ratio of T _reg to Th17 cells in peripheral blood and is characterized by a proinflammatory cytokine microenvironment, which supports the continued generation of Th17 cells.