AGING AFFECTS ORAL TOLERANCE INDUCTION BUT NOT ITS MAINTENANCE IN MICE

B6D2F1 mice, which are very susceptible to tolerance induction by a si ngle gavage with 20 mg of ovalbumin (Ova) at age 8 weeks, become less susceptible at age 25 weeks and totally refractory at age 70 weeks. Ho wever, 70-week-old mice may be rendered tolerant by repeated ingestion of Ova. Mice orally exposed to Ova at age 8 weeks remain tolerant at age 70 weeks. The isotypic pattern of anti-Ova antibodies formed by or ally-tolerant and normal mice after immunization is similar and all is otypes are equally suppressed by oral tolerance. In old mice, oral exp osures to Ova alone triggered an early transient antibody response; so me of these responding animals were, nevertheless, tolerant to subsequ ent parenteral injection of Ova in adjuvant. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.