Pretreatment of mice with rmIL-12 protects against subsequent rmIL-12–induced toxicity. Female C3H/Hej mice received a single subcutaneous injection of rmIL-12 (0.5 or 1 μg) or vehicle 7 days before consecutive dosing with rmIL-12 at the same dose (days 0 to 5). The percent survival of vehicle and rmIL-12 primed mice receiving either 0.5 μg (A) or 1 μg (B) of rmIL-12 is shown (n = 8 per treatment group). The results are representative of three separate experiments. (A) (□), Vehicle day −7; (▪), rmIL-12 day −7. (B) (○), Vehicle day −7; (•), rmIL-12 day −7.