The influence of antigen digestion on orally induced immunity and tolerance

1. Pepsin-digested form of OVA has approximately the same molecular weight as native OVA, but differs in charge and isoelectric focusing point. 2. Pepsin-treated OVA retains most of the native OVA T- and B-cell determinants. 3. Delayed-type hypersensitivity response is suppressed when pepsin-treated OVA is administered i.p. to naive mice. 4. Cimetidine treatment of mice prior to ingestion of OVA shows decreased tolerance, while oral administration of pepsin-treated OVA to cimetidine-treated mice leads to a complete immune unresponsiveness; this suggests an important role for gastric digestion in orally induced immune tolerance.