Hep-2 cells expressing transiently the adenovirus-5 E4-ORF3 protein were analyzed by indirect immunofluorescence using a primary PML monoclonal Ab. Distinct PML-stained cell preparations were labeled with a highly pre-absorbed donkey anti-mouse secondary antibody conjugated to FITC (Jackson ImmunoResearch, code number 715-095-150). Fluorescence images were analyzed in confocal microscopy using a confocal laser scan fluorescence-inverted microscope (LSM 410, Zeiss). Confocal images represent single optical sections. Image analysis was subsequently entered into Photoshop where images were processed and magnified. PML and PML-associated macromolecular complexes have been implicated in mediating transcriptional regulation, suppressing cell cycle progression, inducing apoptosis or cellular senescence, and regulating viral propagation.