An inverse correlation of human peripheral blood regulatory T cell frequency with the disease activity of ulcerative colitis

Evidence suggests that CD4⁺CD25⁺ regulatory T cells play a crucial role in the suppression of intestinal inflammation. However, their role in the suppression of inflammatory bowel disease has not yet been addressed. We examined the proportion of regulatory T cells in inflammatory bowel disease. First, we isolated CD4⁺CD45RO⁺CD25⁺ T cells from the peripheral blood of healthy persons and showed that these cells suppressed T cell proliferation profoundly and expressed FoxP3 abundantly, revealing that they are regulatory cells. Then the proportion of CD45RO⁺CD25⁺ in peripheral blood CD4⁺ T cells was analyzed in patients and healthy controls by flow cytometry. CD4⁺CD45RO⁺CD25⁺ T cell frequency was significantly lower in active ulcerative colitis than in the control and inactive ulcerative colitis. CD4⁺CD45RO⁺CD25⁺ T cell frequency was inversely correlated with the clinical and endoscopic severity of ulcerative colitis. These results suggest that a deficiency of regulatory T cells is associated with the progression of ulcerative colitis.