Plg deficiency delays clearance of apoptotic cells in vivo. (A-B) Cell Tracker Green CMFDA-labeled mouse apoptotic thymocytes were injected IV into Plg^+/+ and Plg^−/− mice. (A) Fluorescent microscopic images in duplicate (top and bottom panels are from 2 different Plg^+/+ and 2 different Plg^−/− mice) showing green-labeled apoptotic thymocytes trapped in the marginal zone of harvested spleens. Images with original magnification of ×20 were captured at room temperature under a Leica DMR upright microscope using an α Retiga EXi Cooled CCD camera and Image-Pro Plus software. The 4′,6 diamidino-2-phenylindole (blue) stains nuclei of splenic cells. Images are representative of 5 Plg^+/+ and 5 Plg^−/− mice. (B) Quantification of apoptotic thymocytes as areas of fluorescence in the spleens of Plg^+/+ and Plg^−/− mice. Bars are mean ± SD of average green fluorescence area per microscopic field. Three to 5 microscopic fields were counted from 5 mice per group. (C-D) Cell Tracker Green CMFDA-labeled apoptotic thymocytes were injected into the peritoneum of Plg^+/+ or Plg^−/− mice. Peritoneal cells were collected 1 hour postinjection and analyzed by flow cytometry. (C) A representative flow cytometry histogram comparing the fluorescence intensity of peritoneal lavage cells and showing the enhanced accumulation of thymocytes in Plg^−/− mice compared with Plg^+/+ mice. (D) Quantitative analysis of cells recovered from peritoneum of Plg^+/+ or Plg^−/− mice. Fluorescent cells with MFI are gated and MFI values derived from these cells are used in the calculation. Bars are mean ± SD of average green fluorescence (n = 3).