Figure 4.

Inhibition of T helper (Th) effector cell development by ganglioside-treated bone-marrow-derived dendritic cells (BMDC) persists despite the addition of exogenous co-stimulation and exogenous IL-12. (a) B6 AND T-cell receptor T cells were stimulated with 50 μm GD1a-treated or untreated control BMDC and pMCC as in Fig. 2, except exogenous 5 ng/ml interleukin-12 (IL-12) or 5 μg/ml exogenous CD28 antibody (clone 37.51) was added as indicated, in addition to control cells which were cultured under neutral conditions as in Fig. 2(a). After 4 days the T cells were harvested and equal numbers were re-stimulated with pMCC and T-cell-depleted spleen cells and interferon-γ (IFN-γ) secretion in the supernatant was assessed by ELISA after 2 days as described for Fig. 2. (b) B6 AND T-cell receptor cells were primed with control or GM1-treated BMDC and pMCC with exogenous IL-2 as in Fig. 2 for 5 days. The cells were then harvested and re-stimulated with pMCC and T-cell-depleted antigen-presenting cell with or without exogenous IL-2 (25 U/m) during re-stimulation. After 48 hr, supernatants were collected and assayed by ELISA as described. *P < 0·005 for all groups compared with control. These data are representative of three independent experiments.