The cytokine production levels of MNCs were also evaluated under stimulation with other agents. Liver MNCs stimulated with concanavalin A (ConA), a T-cell stimulant23, proliferated well both in the vehicle and α-GalCer groups (Fig. 7a,b), and the levels of IFN-γ produced by these cells were comparable between the two groups (Fig. 7c). However, the IL-4 levels in the α-GalCer group were significantly lower than those in the vehicle group (Fig. 7d). Similar cytokine responses were observed when liver MNCs were stimulated with an anti-CD3 Ab. Although the levels of IFN-γ produced by liver MNCs did not differ between the two groups, the IL-4 levels in the α-GalCer group were significantly lower than those in the vehicle group (Fig. 7e,f). This suppression of IL-4 production was also observed in B6 mice, following the repeated administration of α-GalCer (Fig. 7c–f).Figure 7Th2 but not Th1 immune responses are suppressed by repeated alpha-galactosylceramide (α-GalCer) injections. Microphotographs of liver mononuclear cells (MNCs), stimulated by concanavalin A (ConA) in the (a) vehicle and (b) α-GalCer groups (original magnification, 100×). IFN-γ production and IL-4 production from liver MNCs, stimulated with (c,d) ConA or (e,f) anti-CD3 antibody for 48 hours in (NZB/NZW) F1 (BWF1) mice treated with α-GalCer or vehicle, and C57BL/6 J (B6) mice treated with α-GalCer (n = 4–5 in each group). **p < 0.01, ***p < 0.001 compared with the vehicle group of BWF1 mice. ††p < 0.01 compared with the α-GalCer group of BWF1 mice.