Confirming siRNA-induced knockdown of DNase X by immunofluorescence. (a) THP-1 cells pretreated with 50 nM nontargeting siRNA (positive control), THP-1 pretreated with 50 nM siRNA targeting DNase X, and HeLa cells (negative control) were immunostained with the anti-DNase X antibody and secondary fluorescent antibody. Cells were imaged by Epi-fluorescence microscopy that visualizes DNase X throughout cell bodies. (b) Fluorescence intensities of the images in grayscale values were measured for the quantification. n = 30. The result showed that the expression level of DNase X in THP-1 cells was significantly reduced by siRNA knockdown. All significance values (P values) were evaluated by two-tailed tests.