Induction of Tr cells by immature DCs. Peripheral blood CD4⁺CD45RO^– T cells were stimulated 3 times with immature or mature allogeneic DCs. T cells were collected and tested for their ability to suppress responses of autologous CD4⁺ T cells. (A) Thawed CD4⁺ T cells were stimulated with mature DCs alone (MLR) or in the presence of T_(imm) or T_(mat) cell lines at a 1:1 ratio. [³H]-Thymidine was added at the indicated time for an additional 16 hours. (B) In parallel, supernatants were collected after 72 hours and analyzed by ELISA to determine levels of IFN-γ. (A-B) Results are representative of 17 independent experiments.