CTLA4-KDEL acts on DCs via an IDO-independent mechanism in affecting allogeneic T-cell proliferation. (A) CTLA4-KDEL or mock-KDEL–transfected DCs were cocultured with allogeneic T cells in the presence of a range of concentrations of human Ig or CTLA4-Ig. 3H-thymidine incorporation was measured on day 5. (B) The effect of the IDO antagonist, 1-MT, was determined in a parallel set of cultures using a fixed concentration of 10 μg/mL for both CTLA4-Ig and human Ig. 3H-thymidine incorporation was determined on day 5. The results shown on a log scale are expressed as the mean ± SD of triplicate wells from a representative experiment. (C) The up-regulation of IDO transcription in DCs following CTLA4-Ig crosslinking was studied. DCs were isolated from MLRs, which had been treated with human Ig (lane 1) or CTLA4-Ig (lane 2) or from MLRs set up with unmodified DCs (lane 3), mock-KDEL (lane 4), and CTLA4-KDEL (lane 5) transfected DCs. These were analyzed for expression of IDO mRNA by RT-PCR followed by probing with IDO-specific probe (β-actin was used as a control). These data are representative of 3 independent experiments.
