Figure 1. Human CD4⁺CD25^hi Tregs turn over rapidly in vivo.

Freshly isolated PBMCs from healthy individuals were stained for CD4/CD25/CD127/Foxp3 and Ki67 following the standard protocol. Tregs were identified as CD25^hi, Foxp3⁺, and CD127^lo (for details, see Supplemental Figure 1). (A) Expression of Ki67 on CD4⁺CD25^hi, CD4⁺CD25^int, and CD4⁺CD25^– cells from a representative sample. Numbers denote the percentage of cells expressing Ki67 relative to the control gate set with an irrelevant antibody. FSC, forward scatter. (B) Cumulative data showing the percentage of Ki67⁺ cells in each subset. Each symbol represents a different individual (n = 10 per group), and the mean percentage is shown as a horizontal line. Significance was determined by paired t test. (C) Graphs show expression of Ki67 in Treg and non-Treg populations examined over the course of 4 months in 3 individuals.