uPAR inhibits the phagocytosis of apoptotic cells. (A,B) Expression of uPAR is decreased in apoptotic neutrophils. Viable or apoptotic neutrophils were stained with anti-uPAR antibodies and expression of uPAR determined by confocal microscopy (A) or flow cytometry (B). The images were acquired using double bidirectional scans of viable and apoptotic neutrophils with a Leica DMIRBE inverted epifluorescence/Nomarski microscope outfitted with Leica TCS NT laser confocal optics (Leica Inc). The levels of fluorescence were averaged using SimplePCI software (Compix). Images were processed using IPLab Spectrum and Adobe Photoshop (Adobe Systems) software. (C) suPAR inhibits phagocytosis of apoptotic cells. A total of 1 μg/mL suPAR or BSA was added to cultures of apoptotic WT neutrophils, and macrophages and phagocytosis assays were performed.