Diminution of Circulating CD4⁺CD25^high T Cells in Naïve Crohn’s Disease

Crohn’s disease is considered to be caused either by an excess of T-cell effector functions and/or by a defective regulatory T-cell compartment. The aim of this study was to assess in Crohn’s disease the frequency of circulating CD4⁺CD25^high T cells that possess regulatory T-cell functions and CD4⁺CD25^low T cells that contain activated T cells. Flow cytometry of peripheral blood was used to assess CD4⁺CD25^high and CD4⁺CD25^low T-cell frequencies in a cohort of 66 patients with Crohn’s disease in comparison to 19 patients with ulcerative colitis and 31 healthy individuals enrolled as controls. The CD4⁺CD25^high T-cell frequency was significantly lowered in naïve Crohn’s disease (P = 0.013) and in ulcerative colitis (P = 0.001). CD4⁺CD25^low T-cell frequency was increased in Crohn’s disease (P = 0.0001) and in ulcerative colitis (P = 0.0002). Both CD4⁺CD25^high and CD4⁺CD25^low T-cell frequencies are altered in naïve Crohn’s disease resulting in an imbalance between both populations and a relative contraction of the CD4⁺CD25^high T-cell population.