Effect of S1P on T-cell proliferation induced by DCs. Allogeneic iDCs were incubated with T cells for 3 days in media supplemented with serum in the absence or presence of 1 μg/mL LPS (to generate mDCs). These cultures were either left intact or were incubated with 0.01 to 1 μM S1P for 3 days. At this time, 1 μCi (0.037 MBq) [³H]thymidine was added, and the cultures were incubated for an additional 6 hours before harvesting (A). The same experiment was conducted in SFM (B). T cells were pretreated with PTX and then incubated with DCs in the presence of serum (C). Control samples include T cells alone, iDCs alone, iDCs incubated with 1 μg/mL LPS, and T cells incubated with 1 μg/mL LPS in the presence or absence of S1P. Error bars indicate means ± SD.