ATF3 is expressed in MCs after growth factor or FcϵRI activation. (A) Mouse BMMCs were starved of growth factors for 6 hours, then sensitized with anti-DNP IgE and stimulated with DNP–bovine serum albumin (BSA; 100 ng/mL), IL-3 (30 ng/mL), or SCF (50 ng/mL) for 0, 0.25, 0.5, 1, 2, 4, 6, or 18 hours. RNA isolated from these cells was analyzed by real-time reverse transcription–PCR. ATF3 expression was normalized to elongation factor-1 α levels. Error bars represent SE from 3 independent experiments. (B) Mouse BMMCs were sensitized with DNP-BSA (100 ng/mL), IL-3 (30 ng/mL), or SCF (50 ng/mL) for 0, 0.25, 0.5, 1, 2, 4, 6, or 18 hours. Protein was extracted from whole cells and separated by sodium dodecyl sulphate–polyacrylamide gel electrophoresis, and ATF3 was detected with specific antibody. (C) Mouse BMMCs were sensitized with anti-DNP IgE and stimulated with DNP-BSA (100 ng/mL) for 0, 0.5, 2, or 6 hours. Cells were fixed in paraformaldehyde and incubated with rabbit anti-ATF3 antibody. Antibody labeling was detected with boron-dipyrromethene–conjugated goat anti–rabbit antibody. Original magnification ×600.