Antigen processing and uptake from the intestinal tract.

We have attempted, in this discussion, to summarize the processes and evidence for absorption of antigenic macromolecules in both animals and humans, comparing the infant to the adult. The mature gut retains the capacity to absorb macromolecules by an energy-dependent pinocytotic mechanism similar to that described for the transport of immunoglobulins and other enteric antigens in certain mammalian species in the neonatal state. The vast majority of adults show no ill effects as a result of this physiologic phenomenon. However, when increased (pathologic) quantities of antigenic macro-molecules gain access to the body because of a derangement in the intraluminal digestive process, or because of a defect in the mucosal barrier, both of which are present in the immature intestine, macromolecular absorption may be altered and result in either local intestinal or systemic disorders.