Immunosuppressive functions of TIDC depend on arginase-1 activity. (a) Expression of arginase-1 was evaluated in 4T1 tumor derived TIDC and in spDC by WB. Lysate of total liver was used as a positive control. (b) CD3/CD28-stimulated T cells were cultured alone, with TIDC or spDC. After 5 days, supernatants were collected and concentration of ornithine and arginine was quantified by HPLC. Columns represent the mean of the concentration and error bars the SEM. (c) Total T cells were stained using CellTrace Violet Cell Proliferation Kit, stimulated with CD3/CD28 beads and cultured for 5 days with TIDC or spDC in presence or absence of nor-NOHA, arginase-1 inhibitor. The proliferation was defined by flow cytometry and analyzed by ModFit software. The percentage of inhibition for each condition was calculated based on the proliferation index of stimulated T cells (representative of 5 experiments).