CD8 T cells inhibit the expansion of alloreactive Th2 cells through their capacity to rapidly eliminate allogeneic DCs. WT, CD8^–/–, or CD8^–/– transferred with WT CD8 T cells were injected with CFSE^low-labeled syngeneic B6 DCs and CFSE^high-labeled semi-allogeneic CB6F1 DCs. (A) Draining lymph nodes were harvested 72 hours after injection and analyzed for the presence of CFSE-labeled cells. Cells were gated on CD11c^pos, MHC-II^high, and CFSE^pos cells. Percentages of CFSE^high CB6F1 cells among total CFSE^pos cells are indicated. Results are expressed as mean plus or minus SEM of 4 mice per group. (B) The kinetics of IL-4 mRNA expression were analyzed in purified CD4⁺ T cells. (C) CD4 T cells (2 × 10⁵/well) were purified from the draining lymph nodes harvested 6 days after immunization, and cultured in the presence of BALB/c APCs. IFN-γ and IL-4 production were measured by ELISA in 72-hour culture supernatants. Results are expressed as mean plus or minus SEM of 5 mice per group. (D) Pooled CD4⁺ T cells from immunized mice were stimulated with T-cell–depleted BALB/c splenocytes in the presence of anti-CD28 mAb for 8 hours. Intracytoplasmic staining for cytokines was then performed as indicated in “Materials and methods.” Percentages of CD69^pos CD4⁺ T cells producing IFN-γ or IL-4 are mentioned. Data are from 1 representative experiment of 3 performed.