FIG. 11.

(A) Syk^−/− macrophages display reduced phosphorylation of p42 Erk-2 after FcγR engagement. Activation of Erk-2 MAPK was visualized by the phosphorylation-induced mobility shift. Macrophages were allowed to bind to IgG-RBC, and after the indicated incubation times, cells were lysed and tested for the presence of doubly threonine-tyrosine-phosphorylated forms of Erk-2 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. (B) Induction of NOS2 (iNOS) by LPS-gamma interferon is normal in Syk-deficient macrophages. Macrophage cultures were induced with 10-μg/ml LPS and 2-U/ml gamma interferon for 16 h. At the end of the incubation period, cells were lysed and probed for the presence of NOS2 by Western blotting. WT, wild type.