Autocrine IL-10 is required for the differentiation of T_(imm) cells by immature DCs. Peripheral blood CD4⁺CD45RO^– T cells were stimulated with immature allogeneic DCs in the absence or presence of anti–IL-10R or control IgG mAbs (30 μg/mL). After 3 rounds of stimulation, T cells were collected and tested (A) for their ability to proliferate in response to mature DCs and (B) to suppress the response of autologous CD4⁺ T cells. [³H]-Thymidine was added after (A) 48 hours and (B) 72 hours for an additional 16 hours. In parallel, supernatants were collected after (A) 48 hours and (B) 72 hours, and IFN-γ secretion was measured by ELISA. Results are representative of 3 independent experiments.