Figure 5: Tolerogenesis by CpG and GpC requires TRIF but not TLR3 or TLR4 signalling.

(a) pDCs from WT or genetically deficient mice were treated with 10 μg ml⁻¹ CpG (H-CpG), or with 1 or 10 μg ml⁻¹ GpC (L-GpC and H-GpC, respectively) and cotransferred with a majority fraction of spontaneously immunogenic CD8⁻ DCs. The asterisks indicate the occurrence of a positive skin test reaction (*P<0.01 and **P<0.001; experimental versus control footpads; two-tailed paired t-test), and data are mean values±s.d. of three experiments. (b) IDO1 functional activity is induced by high-dose CpG and by both low- and high-dose GpC administrations to Tlr3^−/− or Tlr4^−/− but not Ticam1^−/− mice. Enzyme activity was measured in terms of kynurenine production by the pDCs treated with CpG or GpC. Data are means±s.d. of three experiments. P<0.01 (treatment versus none; Student's t-test).