Gut flora antigens are not important in the maintenance of regulatory T cell heterogeneity and homeostasis

CD25+ regulatory T cells (Treg) are a heterogeneous population that exists as CD44low and CD44high cells. Here we report that while both CD44low and CD44high Treg are anergic and express similar levels of Foxp3, CD44high Treg are highly proliferative in vivo and are more potent suppressors in vitro than CD44low Treg. From analysis of the properties of Treg derived from germ-free mice, it was concluded that peptide antigens derived from intestinal microorganisms are not essential for the generation, in vivo proliferation or suppressive activity of Treg. Our results suggest that gut flora antigens play little or no role in the heterogeneity and homeostatic regulation of Treg.