The intestinal mucosal barrier to intact antigenic protein. Difference between colon and small intestine.

The integrity of the normal mature intestinal mucosal barrier to unaltered proteins was evaluated with tritiated bovine albumin in rats. Intact H3-BSA placed into either colon or small intestinal lumen regularly reached the bloodstream in quantities sufficient to be antigenic or toxigenic, although the fraction of H3-BSA absorbed from the colon (0.13 per cent) was significantly smaller than that absorbed from the small intestine (1.7 per cent). These studies support the possibility that uptake of ingested or bacterial antigens from the normal gut may be involved in the pathogenesis of local intestinal and systemic disease in man.