Antigen uptake in the gut: immunologic implications

Since the principal function of the gastrointestinal tract is that of digestion and absorption of nutrients, it is often assumed that intraluminal protein antigens are completely digested and thus are not transported in appreciable quantity across the epithelium into the lamina propria or systemic circulation. There is now, however, increasing experimental and clinical evidence to suggest that large antigenic molecules can penetrate the intestinal epithelial surface in quantities of no nutritional importance, but possibly immunological significance(1-3). In this review Allan Walker discusses our current understanding of small intestinal permeability to antigens and the potential importance of excessive absorption of macromolecules in mechanisms of immunologically mediated clinical disease.