Figure 4.

Orn Activates IDO1 Signaling and Confers IDO1-Dependent Immunosuppressive Properties in DCs

(A) Immunoblot analysis of phosphorylated IDO1 (pIDO1) and total IDO1 in cell lysates of DCs incubated for different times with TGF-β or Orn (100 μM).

(B) Real-time PCR analysis of Ptpn6 and Tgfb1 transcripts in WT DCs stimulated with TGF-β or Orn (100 μM) or in Itgax-cre;Arg^fl/fl DCs stimulated with TGF-β for 18 hr. Data are normalized and presented as in Figure 1A. ^∗p < 0.05 and ^∗∗p < 0.01 (unpaired Student’s t test; cytokine- or Orn-treated versus untreated samples).

(C) In vivo suppression of the activity of HY-pulsed WT CD8⁻ DCs into WT recipient mice, in combination with a minority fraction (5%) of CD8⁻ DCs from either WT or Ido1^−/− mice with no conditioning (unt, untreated) or conditioned in vitro with TGF-β or Orn (100 μM) for 24 hr; analysis of skin reactivity of recipient mice to the eliciting peptide at 15 days is presented as change in footpad weight. ^∗∗p < 0.01 and ^∗∗∗p < 0.001 (paired Student’s t test; mean weight of experimental versus control footpads). Data are from one experiment representative of two (A) or three (B and C; means ± SD of triplicates in B and six samples in C).