DD is internalized only by activated T cells. Resting and activated T_eff and T_reg cells were incubated with DD (0, 10, and 1000 ng/mL; 16 hours) and stained with anti-DD. In resting T_reg, only high doses of DD gave a punctual staining pattern (white arrow, upper panels). Activated T_eff and T_reg revealed a dose-dependent submembrane accumulation of DD (white arrows, middle and lower panels). At higher concentrations, DD was also detected in the perinuclear area (red arrow, middle panel).