IgG-APS–induced mitochondrial fragmentation. (A) Monocytes were plated in glass-bottomed Petri dishes in phenol red-free RPMI 1640, pretreated for 15 minutes with 50nM MitoTracker Red (excitation 581 nm/emission 644 nm), and then incubated for 6 hours with NHS-IgG or APS-IgG at 37°C in a humidified 5% carbon dioxide atmosphere. Cells were imaged in vivo at 1-hour intervals by confocal microscopy under exactly identical instrument settings for all stimuli. Samples were viewed with an EC Plan-Apochromal 63×/1.40 numerical aperture oil objective. Fragmented mitochondria were prevalent after 2 hours of APS-IgG treatment. CoQ₁₀ pretreatment prevented mitochondrial fission and restored the mitochondrial size found in untreated or IgG-NHS–treated monocytes. (B) Percentage of cells with fragmented mitochondria at each time point is shown. (C-D) Analysis of mitochondrial morphologies by computer-assisted morphometric analyses that calculated the number of mitochondria per cell and their area. Asterisks (*) indicate significant differences (at P < .05) versus IgG-NHS–treated cells.