Figure 3. In vitro ricin-induced apoptosis of THP-1 cells.

mAbs were assessed for their capacity to protect THP-1 human monocytes from apoptosis in the presence of ricin. Ricin (2.5 µg/ml; 38 nM) was incubated with indicated mAbs (20 µg/ml; 133 nM) for 30 min, and then added to THP-1 cells (5×10⁵/200 µl). The cell-mAb mixtures were incubated for 5 h at 37°C, then stained with FITC-Annexin V to assess apoptosis, as described in Materials and Methods. As controls, cells were treated (+ R) or not (− R) with ricin. Each bar represents the average of two replicates plotted as the mean with SEM. Abbreviations: R, ricin. This experiment was repeated 4 times.