LPS stimulation results in ERK phosphorylation of Bim. (A,B) wt or nfkb1^−/− B cells were cultured for 2 hours without or with LPS in the absence or presence of PD98059. Cell lysates were subjected to 2-dimensional gel electrophoresis and Western blotting using Bim-specific antibodies. The data are representative of 5 experiments. (C) Western blots for phospho–c-Raf, phospho-ERK, and ERK in wt and nfkb1^−/− B cells stimulated with anti-IgM antibodies. Data are representative of 3 experiments. (D) Apoptosis in wt and nfkb1^−/− B-cell cultures untreated or stimulated for 48 hours with LPS, anti-IgM antibodies, or both agents. The data represent the mean plus or minus SEM from 4 experiments. (E) Bim Western blots on 2-dimensional gels for wt and nfkb1^−/− B cells left untreated or stimulated (2 hours) with anti-IgM antibodies in the absence or presence of LPS. Data are representative of 3 experiments. The symbols “+” and “−” (panels A, B, and C) refer to the anode and cathode, respectively, and numbers refer to Bim isoforms.