Selective expression of LAP and CD121b allows for separation of Tregs from non-Tregs in ex vivo expansion cultures. (A) Percentage of CD4+LAP+ cells after 48 hours of restimulation of day 14 and 21 expansion cultures. (B) Day 14 expansion cultures generated in the absence (CD25+/NONE) or presence (CD25+/RAPA) of rapamycin were restimulated for 48 hours with anti-CD3/CD28. LAP+/LAP− and CD121b+/CD121b− fractions were then purified with magnetic beads and analyzed by flow cytometry for FOXP3 expression. Number in each quadrant represents the percentage of total population. (C) Percentage of CD4+FOXP3+ and (D) cell yield after purification of LAP+ cells from restimulated 14-day expansion cultures. Horizontal lines in panels A, C, and D represent the mean of each group.