Abstract
Secretory immunoglobulins may decrease bacterial proliferation in the gut and prevent uptake of ingested food antigens. Using a rat model, we have shown that protein antigens [horseradish peroxidase (HRP) and bovine serum albumin (BSA)] are taken up from the small intestine by pinocytosis and that immunization (oral>>parenteral) prevents absorption. To investigate the specific mechanism whereby immunization interferes with absorption, gut sacs from rats shown to have local antibodies (HRP or BSA) after repeated intraperitoneal injections were incubated with the corresponding radiolabelled antigen for intervals up to 3 hrs. In comparison to controls, gut sacs from immunized rats showed: a) rapid binding of labelled antigen to antibody on the intestinal cellular surface, b) enhanced (10X) breakdown of specific antigen, c) no breakdown of unrelated antigens, and d) decreased binding of antigen to intestinal cell membrane. These data suggest the following mechanism for intestinal antibody control of antigen absorption. Initial exposure of gut sacs to antigen leads to rapid association with antibodies on the mucosal surface which results in decreased pinocytosis of antigens by intestinal cells. Antigen-antibody complexes immobilized on the surface of the gut are then degraded by local proteases. The site of degradation is at the level of the glycocalyx or the cell surface membrane.
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Walker, W., Wu, M., Bloch, K. et al. INTESTINAL ANTIBODY FUNCTION: Role in control of antigen absorption in the small intestine. Pediatr Res 8, 420 (1974). https://doi.org/10.1203/00006450-197404000-00482
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DOI: https://doi.org/10.1203/00006450-197404000-00482