miR-155 expression in Treg subsets. Naive Tregs, effector/memory Tregs and naive conventional CD4⁺ T cell subsets were FACS sorted based on the phenotype indicated in the text. miR-155 expression was normalized to RNU44 (small-nucleolar RNA) and represented as fold change compared with naive CD4⁺ T cells. The statistical analysis used was non-parametric 1-way ANOVA Mann Whitney U test (Prism 4.0, GraphicPad).