Quantitative deficiency in blood CD4⁺CD25⁺ T cells in patients with symptomatic MC. PBMCs were stained with PC5-labeled anti-CD4 together with FITC-labeled anti-CD25 or an isotypic control. The frequency of Treg cells was determined after gating on CD4⁺ T cells as the percentage of the brightest CD25⁺ population. Horizontal bar indicates the mean in each group.