Regulation of IL-10 production in CD8 T cells. (A) OT-1 cells were stimulated with OVA²⁵⁷ alone or with IL-4, IL-12, and 10 nM DEX. After 4 days cells were restimulated before intracellular cytokine staining for IFN-γ, IL-4, and IL-10. The percentage of cytokine-producing cells is shown. IL-4 staining was less than 1% in all CD8 populations (not shown). (B) IL-10 secretion of naive OT-1 cells or those primed for 4 days with peptide ± IL-4/IL-12/DEX after restimulation with splenic APC + OVA²⁵⁷. (C) Comparison of CD8 (top row) with CD4 (bottom 2 rows) differentiation in MLRs using BALB/c CD4 or CD8 cells + C57BL/6 DCs. Cells were analyzed after 7 days as in panel A. IL-4 staining was less than 1% in all CD8 populations. (D) Generation of IL-10–producing cells from differentiated Tc1 effectors. OT-1 Tc1 cells were generated by peptide stimulation for 4 days, washed, and put into secondary culture with IL-15 + IL-7 ± IL-4/IL12/DEX. Four days later, cells were analyzed as in panel A. All data are representative of 4 independent experiments with similar results; in panel B, means ± SEMs from 4 independent experiments are shown.