U937 cells were fixed with 4% PFA for 10min at room temperature,permeabilized with 0.1% PBST for 20 min at room temperature, and incubated in 5% BSA blocking buffer for 30 min at room temperature. Cells were then stained with APAF1 Polyclonal Antibody(bs-0059R-FITC)at 1:50 dilution in blocking buffer and incubated for 30 min at room temperature, washed twice with 2%BSA in PBS. Acquisitions of 20,000 events were performed. Cells stained with primary antibody (green), and isotype control (orange).