LPS-treated DCs induced CD4-independent CD8⁺ T-cell proliferation whereas pretreatment of DCs with MPA abolished this capacity. MPA-DCs and mDCs designate DCs matured with LPS (50 ng/mL) for 2 days in the presence or absence of MPA (100μM). (A) MPA-DCs induced CD8⁺ T-cell unresponsiveness. mDCs and MPA-DCs obtained after monocyte adhesion (filled bars) or after CD14-positive selection (hatched bars) were cocultured for 6 days with allogeneic purified CD8⁺ T lymphocytes at a DC:T ratio of 1:3. T-cell proliferation was measured by incorporation of 1 μCi [3H]-thymidine added for the last 18 hours of culture. (B) Naive and memory CD8⁺ T cells were unresponsive to MPA-DCs. CD8⁺ CD45RA⁺ (filled bars) and CD8⁺ CD45RO⁺ (hatched bars) T cells were isolated from purified CD8⁺ T lymphocytes and then cocultured with allogeneic MPA-DCs or mDCs for 6 days at a DC:T ratio of 1:3. T-cell proliferation was measured by [3H]-thymidine incorporation. (C) IL-2 prevented CD8⁺ T-cell hyporesponsiveness. Purified CD8⁺ T lymphocytes were cocultured with allogeneic MPA-DCs or mDCs in the presence or absence of exogenous IL-2 (100 IU/mL). T-cell proliferation was measured as described above. (D) MPA-DCs induced donor-specific anergy. First coculture of allogeneic CD8⁺ T cells with MPA-DCs was performed, followed by a second stimulation in the presence (black bar) or absence (gray bar) of exogenous IL-2 (100 IU/mL) with mDCs from the donor used in the first coculture. Donor-specific unresponsiveness was assessed by further stimulation using mDCs from the first DC-donor (mDC^a; gray bar) or a third party (mDC^b; hatched bars). T-cell proliferation was measured on day 5 by incorporation of [3H]-thymidine. Results are expressed as mean cpm ± SD obtained from triplicate wells and are representative of 1 of 7 experiments. *P < .05.