Figure 5.

T helper type 17 (Th17) cells derived from BDC2·5 T cells by interleukin (IL)-23 + IL-6 polarization are highly diabetogenic, while regulatory T helper type 17 (T_reg17) cells are induced by transforming growth factor (TGF)-β + IL-6. Spleens were harvested from 6–8-week-old BDC2·5 non-obese diabetic (NOD) mice, and single-cell suspensions were prepared. The cells (2 × 10⁵ cells/well) were cultured in 96-well plates in the presence of PS3 mimotope (1 µM) in complete RPMI-1640 medium at 37°C, 5% CO₂ for 5 days. Cells were either polarized with TGF-β (3 ng/ml) + IL-6 (20 ng/ml) cytokines or IL-23 (10 ng/ml) + IL-6 (20 ng/ml) cytokine cocktails. Cells stimulated with PS3 mimotope without cytokine treatment were used as a control. (a) Cells from various treatment groups were collected on day 5, washed and 5 × 10⁶ cells/mouse were transferred adoptively via tail vein into 5-week-old NOD mice and the diabetes incidence was monitored. All mice injected with IL-23 + IL-6 polarized BDC2·5 cells developed diabetes. The Kaplan–Meier survival estimate was used to determine differences in the two groups. Significant difference was observed between the IL-23+IL-6 and TGF-β+IL-6 groups (P < 0·001). (b) Equal numbers (5 × 10⁶) of Th17_{(TGF-β + IL-6)} and Th17_{(IL-23 + IL-6)} cells were injected into the tail vein of 5-week-old NOD mice. Th17_{(TGF-β + IL-6)} cells blocked disease development. Significant difference was observed between the two groups (P < 0·01).