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 (MDS) 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 age-matched 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.