IgG-dependent extra-phagosomal ROS production. Primed WT mouse bone marrow–derived neutrophils (BMNs) were preincubated with NBT, left untreated (i), or incubated with serum-opsonized S aureus (ii); IgG-opsonized SRBCs (iii); immobilized immune complex IgG-BSA (iv); unopsonized (v) or IgG-opsonized (vi) latex beads; serum-opsonized (vii) or IgG-opsonized (viii) zymosan, as described in “Phagocytosis assays,” and supplemental Methods. Non-phagocytosed S aureus or SRBCs were lysed before processing. Samples were cytospun (i-ii) or allowed to adhere (iii-viii) onto glass coverslips, fixed in 4% paraformaldehyde, washed, and mounted as described in “Phagocytosis assays.” Dark formazan deposition was detected by DIC imaging on a Zeiss LSM 510 META point-scanning confocal microscope. Shown are representative DIC images, including an enlarged section of formazan deposition under each condition. The IgG-SRBC phagosome is indicated by a white star. Scale bars represent 5 μm.