Comparison of Dectin-1 and FcγR-mediated phagocytosis in macrophages, demonstrating that Dectin-1-mediated phagocytosis is Syk-independent. (A) RAW264.7 cells expressing Dectin-1 were incubated with the various inhibitors, as indicated in “Materials and methods,” prior to synchronized uptake of equal numbers of particles of zymosan or antibody-opsonized SRBCs for 30 minutes. The amount of uptake was normalized relative to the DMSO solvent control to allow direct comparison between experiments, although there was no significant difference in uptake between the zymosan or antibody-opsonized SRBCs fed control cells (84.9 ± 5.1 versus 76.24 ± 12.33, respectively). The data presented were pooled from 3 independent experiments and are shown as the mean ± SEM. ^* indicates significant differences (P < .05) in uptake between the 2 receptors; ns indicates not significant. (B) Comparative phagocytosis of unopsonized zymosan and antibody opsonized SRBCs in wild-type (wt) and Syk deficient (Syk^-/-) bone marrow-derived macrophages. Cytochalasin D (CytoD) was added to inhibit phagocytosis, as a control in these experiments. The figure shows the mean ± SEM of data pooled from 3 independent experiments. (C) Anti-p72Syk Western blot demonstrates the presence or absence of Syk in whole-cell lysates, as indicated. Zap70 was also not detected in any of the lysates (data not shown).