Stability of CD147 expression. (A) CD4⁺ T cells, either enriched or depleted for CD25, were stimulated for 48 hours by anti-CD3/anti-CD2/anti-CD28–coated beads at a 1:2 ratio of beads to cells. Resting and activated T cells were then analyzed for their expression of CD25, FoxP3, and CD45RO versus CD147. Mean fluorescence intensities (MFI) in doubly positive cells are indicated. (B) CD4⁺CD25⁺CD147⁺ and CD4⁺CD25⁺CD147⁻ T cells were FACS sorted to > 96% purity as determined by their CD147 expression and activated by CD23/CD3/CD28-coated beads for 48 hours. Expression profiles of CD25, CD147, and FoxP3 under resting and stimulating conditions were analyzed by flow cytometry and compared in histogram-overlay analysis.