Immunization with the insulin B chains, but not the insulin A chain, is effective in preventing IDDM in RIP-NP mice. RIP-NP transgenic mice were immunized with 100 μg of porcine insulin A or B chains in IFA (1:1) once 5 days after LCMV infection, or were fed oral whole-porcine insulin as a positive control (see Methods for feeding protocol). Diabetes was measured weekly by Accucheck (see Methods); the total observation period was 3 months. Group sizes were as follows: 5 mice received insulin A; 6 mice received insulin B; 10 mice received oral porcine insulin (5); 10 mice were untreated controls. Definition of diabetes is blood glucose consistently >350 mg/dL.