CD4+CD25high Foxp3+ regulatory T cells in myelodysplastic syndrome (MDS)

Foxp3+ regulatory T cells (Tregs) play a central role in maintaining immune tolerance. A reduction in the function of Tregs is a key feature of autoimmune diseases, whereas their expansion in malignant diseases leads to the suppression of host antitumor responses. We analyzed the absolute number of CD4(+) and CD8(+) Tregs in the peripheral blood of 52 patients with myelodysplastic syndrome (IMDS) and show a significant correlation between increased number of CD4(+) Tregs and MDS subgroups with 5% or more bone marrow blasts (P<.001), high International Prognostic Scoring System (IPSS) score (P <.001), and disease progression (P <.001), whereas no correlation between CD8(+) Tregs and prognostic variables was observed. The CD4(+) Tregs showed a polyclonal spectratype, and the percentage of the naive subset was significantly higher in the high-risk patients compared with low-risk or healthy agematched donors (P =.032). Our data suggest that CD4(+) Treg expansion is a feature of high-risk MDS and progression to aggressive subtypes of the disease.