Syk is required for normal phosphorylation events after bacterial stimulation. Western blot analysis of (A) c-Cbl or (B) Pyk2 phosphorylation after stimulation of WT or syk^−/− neutrophils with S aureus (Sa) or E coli (Ec) for 10 minutes. For quantitation, c-Cbl and p-c-Cbl were detected on separate gels and were each normalized to actin; p-Pyk2 was normalized to total Pyk2 detected on the same gel. (C-D) Flow cytometric histograms of intracellular (C) p-Erk1/2 at 10 minutes in response to S aureus or at 15 minutes in response to E coli or (D) p-p38 at 20 minutes in response to S aureus or E coli. Histograms of unstimulated WT (black dash) or syk^−/− (filled gray) and stimulated WT (black) or syk^−/− (gray) neutrophils are shown. Time course quantitation is of the MFI. Error bars represent ± SD. *P < .05, **P < .01, #P < .001 by 2-way ANOVA with Bonferroni posttests. All data are representative of 3 or more independent experiments.