Requirements for zymosan activation of Src/Syk signaling. (A) Syk activation was assessed in IFN-γ-primed bone marrow-derived macrophages stimulated with zymosan in the presence of the Src kinase inhibitor, PP2 (25 μM), or the soluble β-glucan, laminarin (0.5 mg/mL). (B) Syk and Src activation was measured in IFN-γ-primed bone marrow-derived macrophages obtained from mice deficient in MyD88, DAP12/FcRγ chain, or CD18 as indicated.