Syk is required for zymosan-induced ROS production. (A) IFN-γ-primed wild-type or Syk^-/- bone marrow-derived macrophages were stimulated with zymosan, IgG-opsonized sheep red blood cells (SRBCs), or phorbol myristate acetate (PMA) as indicated, and generation of reactive oxygen was measured by enhanced chemiluminescence. (B) IFN-γ-primed wild-type or gp91^phox-/- bone marrow-derived macrophages were stimulated with zymosan in the presence or absence of the Syk inhibitor, piceatannol (Pic), or the Src family kinase inhibitor, PP2, and generation of reactive oxygen was measured. (C) IFN-γ-primed bone marrow-derived macrophages were fed zymosan for 15 minutes, and translocation of p47^phox to phagosome membranes and Syk phosphorylation was observed by immunofluorescence microscopy. (D) RAW264.7 macrophages expressing SBP-tagged Dectin-1 were stimulated with fluorescently labeled zymosan for 1 hour, and ROS production was detected by flow cytometry using APF.