Oral tolerance by a high dose OVA in BALB/c mice is more pronounced and persistent in Th2-mediated immune responses than in Th1 responses.

Oral administration of antigen induces an antigen-specific immunologic tolerance and many studies are being carried out to apply this phenomenon to the treatment of autoimmune diseases. In this study, we investigated long-term Th1 and Th2 tolerance in mice given a high dose of orally administered Ovalbumin (OVA). Feeding OVA to BALB/c mice suppressed OVA-specific IgG response and the degree of inhibition was dose-dependent in the range of 2.5-250 mg. Moreover, the state of tolerance established by prior feeding of high dose of OVA was present after 26 weeks. Interestingly, even though both Th subsets were tolerized significantly for a short period, the tolerizing effect was more pronounced and persistent in Th2-mediated immune responses. Thus we speculate that oral administration of a single high dose of OVA induces Th1- and Th2-tolerance by different mechanisms. Our findings could be important in the development of therapeutics for the treatment of autoimmune disease and allergy.