Decrease of CD4+ CD25+ CD127low FoxP3+ regulatory T cells with impaired suppressive function in untreated ulcerative colitis patients

Regulatory T (Treg) cells take part in immune homeostasis and play a pivotal role in maintaining peripheral tolerance. The aim of this study was to evaluate the frequency and function of Treg cells in active and untreated ulcerative colitis (UC) patients. Thirty-two subjects with newly diagnosed UC and 31 age-matched healthy controls were included in this survey. The frequency of Tregs was analyzed with flow cytometry using CD4, CD25, CD127 and FoxP3 markers. We used surface expression of CD4(+), CD25(+) and CD127(low) markers for isolation of a relatively pure Treg population. Suppressive activity of Tregs was determined by measuring their ability to inhibit the proliferation of T responder cells. UC patients had a lower frequency of CD4(+) CD25(+) CD127(low) FoxP3(+) Treg cells. Additionally, Treg cell-mediated suppression was lower in UC patients compared to controls. The frequency and suppressive capacity of Tregs and MFI of FoxP3 were inversely correlated with disease activity. These results suggest that CD4(+) CD25(+) CD127(low) FoxP3(+) Treg cells may contribute to immunopathogenesis of UC, and assessment of Treg cell frequency and function may have clinical value.