Oral tolerance is not influenced by oral application of oil-emulsified proteins.

A 2-week program of feeding protein antigens as an oil-in-water emulsion to naive mice elicited a significant serum IgG antibody response, whereas their aqueous preparations did not at all. The unresponsive immune state that had been developed after feeding aqueous antigen was not disturbed by subsequent oral challenge with the same antigen in the presence of oil. These results suggest that the principle of oral tolerance is a feasible strategy for prophylaxis of hypersensitization to protein antigens, where protein tolerogens, in this case, are to be given without any additives at their first introduction.