Effect of Locally Induced Intestinal Anaphylaxis on the Uptake of a Bystander Antigen

Adult Sprague-Dawley rats weighing 250 gm were immunized with 100 micrograms egg albumin (EA) and alum. Fourteen days later, intestinal anaphylaxis was induced by intraduodenal or intragastric challenge with EA. To test for the changes in vascular and mucosal permeability that accompany anaphylaxis, the rats were injected intravenously with 125I-rat serum albumin (RSA) at the time of challenge and the amount of radioactivity retained in the wall of gut segments, as well as the trichloroacetic acid (TCA)-precipitable radioactivity present in the secretions obtained from these segments, was determined. Enhanced retention of 125I-RSA was found in the wall of the duodenum and first and second halves of the small intestine, and increased amounts of TCA-precipitable radioactivity was found in gut segments obtained from antigen-challenged compared with buffer-challenged rats. In other EA-immunized rats bovine serum albumin (BSA) was administered by gavage 1 hr before challenge with EA. Increased amounts of immunoreactive BSA were detected by radioimmunoassay in the serum of rats subjected to local intestinal anaphylaxis. Possible consequences of the enhanced systemic uptake of protein present during local intestinal anaphylaxis were considered. It was suggested that such proteins might induce an IgE antibody response, thereby broadening the anaphylactic sensitivity of the animal to additional antigens.