After rats were orally administrated with bovine serum albumin (BSA) for 14, 30 and 90 days, we examined the localization of the absorbed intact BSA immunohistologically and the production of the antibody against the absorbed BSA in the intestine.
Light microscopical sections with hematoxylin-eosin (H-E) stain, as compared with normal intestine, revealed an increased number of disrupted goblet cells and extended macrophages in the lamina propria.
By the immunofluorescent method, intact BSA absorbed by the intestine was found in macrophages, intestinal columnar cells, the lateral extracellular spaces between the columnar cells, goblet cells and mucous materials in the lumen.
The cytoplasm of the plasma, macrophages and intestinal columnar cells showed the antibody against BSA.
These findings suggest that orally administrated BSA is absorbed in macromolecular form by the intestine and the antibody against BSA produced in the plasma cells is secreted in the lumen as secretory IgA (SIgA). And consequently, immunocomplexes are formed in the lumen, and there is an increased number of disrupted goblet cells and mucous release.
