Figure 4.

T_reg induced by IDO1-expressing AML-DC inhibit leukemia-specific T-cell proliferation. (A) AML cells were lysed and used for the pulsing of immature normal monocyte-derived DC. The endocytic activity of immature DC was assessed with a PKH26 red fluorescent cell linker kit. Pulsed and not pulsed DC were tested by flow cytometry. The results are representative of three different experiments. (B) Freshly purified normal CD3⁺ T cells were co-cultured with autologous DC, previously loaded with allogeneic necrotic AML blasts, at a 10:1 T cell–to–DC cell ratio. After three rounds of re-stimulation, T cells were collected, purified into different T-cell subsets and used for proliferation assays in response to autologous monocyte-derived DC previously loaded with necrotic AML blasts. As control samples, unloaded monocyte-derived DC were used. AML cells used for DC pulsing were the same cells as those with had been used to generate AML-DC. The results are the mean ± SD of four different experiments. (C) T_regs induced by IDO1-expressing AML-DC were added to cultures consisting of leukemia-specific CD4⁺ T cells and autologous DC previously loaded with necrotic AML cells. The results are the mean ± SD of three different experiments.