Cell culture. RAW 264.7 cells (ATCC, Rockville, MD) were cultured in Dulbecco's modified Eagle's medium supplemented with 10% (vol/vol) heatinactivated fetal bovine serum (Atlanta Biologicals, Lawrenceville, GA), streptomycin (100 lg/ml), and penicillin (100 U/ml) at 37°C in a humidified incubator with 5% CO 2 . Cell number and viability were assessed by trypan blue dye exclusion using a hematocytometer. Prior to exposure of toxins (DON, SG, anisomycin, and ricin) or inhibitors, cells (2.5 3 10 6 ) were seeded and cultured in 100-mm tissue culture plates for 24 h to achieve approximately 80% confluency.