Selective expression of LAP, CD121a, and CD121b on activated Tregs. (A) Flow cytometric analysis of surface LAP, CD121a, and CD121b and intracellular FOXP3 expression on day 14 and day 21 Treg expansion cultures after restimulation for 48 hours with anti-CD3/CD28 (data are from 1 representative donor of 6). (B) Kinetics of LAP, CD121a, and CD121b expression on fresh Tregs stimulated with anti-CD3/CD28 and 100 U/mL IL-2. (C) Costaining of LAP, CD121a, and CD121b on 48-hour restimulated day 14 cultures (data are from 1 donor representative of 6). (D) Expression of LAP, CD121a, and CD121b on 48-hour restimulated day 14 CD4⁺CD25⁻CD127⁺CD45RA⁺ and CD45RO⁺ T cells previously stimulated on day 0 with anti-CD3/CD28 and IL-2 for 5 days in the absence (−) or presence (+) of TGFβ1 and rested in IL-2 until day 12. Data are representative of 3 independent experiments. Number in each quadrant represents the percentage of total population.