Intestinal uptake of macromolecules: effect of oral immunization.

Animals were orally immunized with horseradish peroxidase and bovine serum albumin, and absorption of these antigens was studied. In comparison with controls, a consistent and significant decrease in peroxidase uptake was noted in both germ-free and conventional rats immunized with peroxidase; a similar decrease in serum albumin uptake was also noted in animals immunized with serum albumin. There was no difference in the uptake of an unrelated macromolecule. These observations suggest that local immunization interferes specifically with the intestinal uptake of macromolecular antigens.