pp. manner mediated by phosphatidylserine that appears on the surfaces of infected cells during the process of apoptosis. Many viruses induce Corynoxeine Corynoxeine apoptotic death in sponsor cells, but the physiological indicating of this trend Corynoxeine is not yet recognized (9, 27). HeLa cells infected with influenza A computer virus undergo Fas/Fas ligand-mediated and caspase-dependent apoptosis (7, 25, 28), but the computer virus appears to replicate normally and computer virus progeny are released into the tradition medium (26). Cells undergoing apoptosis are in general rapidly and selectively engulfed by phagocytes (3, 29), and this presumably prevents swelling that would normally be caused by the noxious material of lifeless cells (14, 16, 17). It could thus be reasonably expected that influenza virus-infected cells would be susceptible to apoptosis-dependent phagocytosis. Recently, it was reported that phagocytosis of apoptotic cells prospects to antigen demonstration to lymphocytes; Thbd dendritic cells that phagocytosed influenza virus-infected cells undergoing apoptosis stimulated CD8+ T cells (1, 2). It was shown, on the other hand, that phagocytosis of influenza virus-infected cells by macrophages led to elimination of the computer virus (8). In both cases, virus-infected cells were phagocytosed depending on the event of apoptosis (2, 8). These results suggest that apoptosis of influenza virus-infected cells shields the organism from viral invasion inside a dual manner. Apoptosing cells expose a phagocytic marker(s) on their surfaces, and phagocytes identify this marker and use a specific receptor(s) to engulf the cells showing this marker (14, 16, 17). As a first step toward an understanding of the molecular basis of the phagocytosis of influenza virus-infected cells, we searched for the marker molecule(s) responsible for the acknowledgement of influenza virus-infected cells by macrophages. MATERIALS AND METHODS Illness and growth of influenza computer virus in HeLa cells. HeLa S3 cells were managed in Eagle’s minimal essential medium comprising 10% fetal bovine serum at 37C in 5% CO2. HeLa cells were infected having a wild-type strain of influenza A/Udon/72 (H3N2) computer virus, SP626, at a multiplicity of illness of two, as described previously (7, 28). Virus growth was monitored by either an immunohistochemical analysis or a plaque assay (24). For immunohistochemistry, influenza virus-infected HeLa cells were managed in poly-d-Lys-coated tradition containers, fixed, and permeabilized, as explained previously (8). The cells were treated with an anti-influenza computer virus antiserum which recognizes NP, M1, HA, and NA (19) and then having a fluorescein isothiocyanate (FITC)-conjugated anti-rabbit immunoglobulin G (IgG) antibody (Immunotech, Marseilles, France) and examined by fluorescence and phase-contrast microscopy (BX50 microscope; Olympus, Tokyo, Japan). The amount of computer virus released into the tradition medium was determined by a plaque assay using MDCK cells and indicated as PFU as explained previously (25). Apoptosis analysis. Cell viability and chromatin condensation were analyzed under a microscope after staining cells with trypan blue and Hoechst 33342, respectively. Translocation of the membrane phospholipid phosphatidylserine (PS) from your cytoplasmic to the exoplasmic leaflet of the plasma membrane was determined by circulation cytometry using annexin V, which specifically binds to PS, as explained previously (10, 12). In brief, cells were treated with FITC-labeled annexin V (Bender MedSystems, Vienna, Austria) and propidium iodide, a membrane-impermeative fluorochrome, and analyzed in a circulation cytometer (EPICS-XL; Coulter, Hialeah, Fla.). The cells that were less intensely stained with propidium iodide and thus impermeable by annexin V were gated and analyzed for the amount of certain FITC-annexin V. To inhibit apoptosis, z-VAD-fmk (23) (Peptide Institute, Osaka, Japan), an inhibitor of caspases, was added to the medium when virus-infected cells were put into the tradition dishes. Macrophage preparation and phagocytosis assay. Macrophages were isolated from your peritoneal cavities of thioglycolate-treated BDF1 mice and managed in RPMI 1640 comprising 10% fetal bovine serum at 37C until use, as described previously (4, 21). The phagocytosis assay was performed essentially as explained previously (20). Briefly, HeLa cells were labeled with biotin (NHS-LS-Biotin; Pierce, Rockford, Ill.), mixed with macrophages (at a percentage.
