Figure 5.

T cells primed with GD1a-treated bone-marrow-derived dendritic cells (BMDC) inhibit interferon-γ (IFN-γ) production by previously primed Th effector cells. B6 AND T-cell receptor T cells were stimulated with GD1a treated or untreated control BMDC and pMCC as in Fig. 2 for 4 days. The T cells from each group were harvested and re-stimulated with T-cell-depleted splenocytes and pMCC. (a) Increasing numbers of T cells originally primed with GD1a-treated BMDC were mixed with a fixed number of control T cells (5 × 10⁵) primed with untreated BMDC (No GD1a) before re-stimulation. These cells were re-stimulated for 48 hr with T-cell-depleted splenocytes in the presence of pMCC and IFN-γ production was measured by ELISA. *P < 0·01 for the indicated groups compared with control. (b) T cells primed with control, untreated BMDC or as above were harvested after 5 days and labelled with CFSE, whereas T cells primed with ganglioside-treated DC were harvested in parallel and left unlabelled to distinguish the two populations of T cells. The cells were then re-stimulated for approximately 24 hr in the absence or presence of equal numbers of T cells primed with GD1a-treated BMDC (unlabelled by CFSE). Intracellular IFN-γ production was assessed by flow cytometry. Key: Left panel (control): CFSE-labelled T cells primed with control BMDC combined with unlabelled T cells primed with control BMDC; right panel: CFSE-labelled T cells primed with control BMDC combined with equal numbers of unlabelled T cells primed with GD1a-treated BMDC. These data are representative of three independent experiments.