Effect of IFN-γ–treated DCs on MBP-specific T-cell proliferation of MS patients. mDCs were generated with CD40L + LPS, treated with IFN-γ, loaded with MBP, and cocultured with autologous peripheral lymphocytes obtained from MS patients (n = 10) (A). Alternatively, IFN-γ–treated MBP-DCs (± 1-MT) of HLA-DR compatible healthy donors were coincubated with H saimiri–transformed MBP-specific T cells (clone ES-BP8T) at a ratio of 1:10 (n = 8) (B) or at increasing ratios (n = 5) (C). For experiment A, controls consisted of MBP-loaded DCs plus autologous peripheral lymphocytes, MBP-DCs only, or lymphocytes only. For experiment B, controls consisted of MBP-loaded (without IFN-γ) or -unloaded DCs (± IFN-γ) plus ES-BP8T cells, ES-BP8T cells only, or MBP-loaded DCs only. Cell proliferation was measured after 4 days. Data represent mean ± SD and are expressed as a percentage of the positive control values (= 100%) (mean stimulation for A: 11 000 ± 5600 cpm and for B-C: 19 200 ± 5500 cpm). No statistically significant difference between the T-cell stimulatory capacity of native DCs and IDO DCs was noted in experiment A. IDO DCs significantly suppressed the T-cell response in experiment B (P = 10^-4).