U937 cells were used 3 days after passaging. Half were activated with IFN-gamma 100 ng/ml for 20 hours and half were used as a control. Cell concentration at the beginning of activation was 2.1 x 105 cells/ml. Brefaldin A was used as an intracellular blocking agent at 1µg/ml, in contact with the cells for 4 to 6 hours. The black line on the graph represents the IgG2b isotype control, the green line shows ab86317 with U937 non-activated cells and the yellow line represents activated U937 cells marked with ab86317 (10µl per test for 5.1 x 105 cells).