Figure 1.

Immunosuppressive activity of BM-derived MDSCs and MSC-1 cells. BM cells were extracted from 6 to 8-week-old C57BL/6 mice and cultured for 4 days in the presence of GM-CSF and IL-6 (40 ng/ml each, except for the control cultures). MSC-1 cells were cultured for 48 h in the presence of 100 μM of 1400 W and 5 μM of BEC (except for control cultures). (A) Nitrite and nitrate concentration based on the Griess reaction. (B) ARG1 activity: one unit (U) of ARG1 activity is defined as the enzyme activity that catalyses the production of 1 μmol urea/min. Filled and empty symbols (■, □) correspond to BM cells and BM-derived MDSC cultures, respectively. Filled and empty symbols (▴, ▵) correspond to MSC-1 cells and 1400 W and BEC-treated MSC-1 cells, respectively. The same nomenclature is used for all figures unless specified. (C, D) Ratios (referenced to the control culture) of Jurkat cell density and viability, respectively. Jurkat cells were cultured for 24 h in the presence of untreated BM cells (Black), BM cells exposed to GM-CSF and IL-6 for 24, 48, 72 or 96 h (hatched) and cytokines (Grey). (E, F) Ratios (referenced to the control culture) of Jurkat cell density and viability, respectively. Jurkat cells were inoculated in the presence of MSC-1 cells (Black) or MSC-1 cells pre-cultured for 12 h in the presence of 1400 W (100 μM) and BEC (5 μM) (White). Ratios are based on the cell density and viability of the control culture, which consists of Jurkat cells inoculated in inserts (500 μl at 0.2 × 10⁶ cells/ml) placed in wells containing 500 μl of complemented culture medium. The same control culture is considered for subsequent cytotoxicity tests.